(Ebook) o reilly oracle pl sql programming

1. [Appendix A] Whats on the Companion Disk?

2. [Appendix A] Whats on the Companion Disk? Table of Contents A. Whats on the Companion Disk?..................................................................................................................2 A.1 Installing the Guide...........................................................................................................................2...............................................................................................................................................................................3 A.2 Using the Guide................................................................................................................................3...............................................................................................................................................................................5 B. Calling Stored Procedures from PL/SQL Version 1.1................................................................................6 B.1 Using Stubs to Talk to ServerSide PL/SQL ....................................................................................7...............................................................................................................................................................................9 B.2 Restrictions on Calling Stored Procedures........................................................................................9 B.2.1 No ServerSide PL/SQL Datatypes..................................................................................9 B.2.2 No Direct Stored Package Variable References ..............................................................10 B.2.3 No Direct Remote Procedure Calls.................................................................................12 B.2.4 No Default Parameter Values ..........................................................................................12.............................................................................................................................................................................14 C. BuiltIn Packages........................................................................................................................................15 C.1 Using the Builtin Packages...........................................................................................................16.............................................................................................................................................................................18 C.2 DBMS_ALERT ...............................................................................................................................18 C.2.1 The REGISTER procedure.............................................................................................18 C.2.2 The REMOVE procedure ................................................................................................18 C.2.3 The REMOVEALL procedure........................................................................................18 C.2.4 The SET_DEFAULTS procedure...................................................................................18 C.2.5 The SIGNAL procedure..................................................................................................18 C.2.6 The WAITANY procedure.............................................................................................19 C.2.7 The WAITONE procedure..............................................................................................19.............................................................................................................................................................................20 C.3 Oracle AQ, the Advanced Queueing Facility ..................................................................................20 C.3.1 DBMS_AQ (PL/SQL 8 Only) .........................................................................................20 C.3.2 DBMS_AQADM (PL/SQL 8 Only)...............................................................................21.............................................................................................................................................................................24 C.4 DBMS_DDL...................................................................................................................................24 C.4.1 The ALTER_COMPILE procedure................................................................................24 C.4.2 The ANALYZE_OBJECT procedure.............................................................................24.............................................................................................................................................................................25 C.5 DBMS_ JOB...................................................................................................................................25 C.5.1 The BROKEN procedure................................................................................................25 C.5.2 The CHANGE procedure................................................................................................25 C.5.3 The INTERVAL procedure .............................................................................................25 C.5.4 The ISUBMIT procedure................................................................................................25 C.5.5 The NEXT_DATE procedure.........................................................................................26 C.5.6 The REMOVE procedure ................................................................................................26 C.5.7 The RUN procedure........................................................................................................26 C.5.8 The SUBMIT procedure.................................................................................................26 C.5.9 The USER_EXPORT procedure.....................................................................................26 C.5.10 The WHAT procedure ...................................................................................................26.............................................................................................................................................................................28 C.6 DBMS_LOB (PL/SQL8 Only).......................................................................................................28 C.6.1 The APPEND procedure.................................................................................................28 C.6.2 The COMPARE function................................................................................................28 C.6.3 The COPY procedure......................................................................................................29 i

3. [Appendix A] Whats on the Companion Disk? Table of Contents C.6.4 The ERASE procedure....................................................................................................29 C.6.5 The FILECLOSE procedure...........................................................................................29 C.6.6 The FILECLOSEALL procedure ....................................................................................29 C.6.7 The FILEEXISTS function.............................................................................................29 C.6.8 The FILEGETNAME procedure .....................................................................................29 C.6.9 The FILEISOPEN function.............................................................................................30 C.6.10 The FILEOPEN procedure ............................................................................................30 C.6.11 The GETLENGTH function.........................................................................................30 C.6.12 The INSTR function ......................................................................................................30 C.6.13 The READ procedure ....................................................................................................30 C.6.14 The SUBSTR function..................................................................................................31 C.6.15 The TRIM procedure .....................................................................................................31 C.6.16 The WRITE procedure..................................................................................................31.............................................................................................................................................................................33 C.7 DBMS_LOCK .................................................................................................................................33 C.7.1 The ALLOCATE_UNIQUE procedure..........................................................................33 C.7.2 The CONVERT function................................................................................................33 C.7.3 The RELEASE function ..................................................................................................34 C.7.4 The REQUEST function.................................................................................................34 C.7.5 The SLEEP procedure.....................................................................................................34.............................................................................................................................................................................36 C.8 DBMS_MAIL.................................................................................................................................36 C.8.1 The SEND procedure......................................................................................................36.............................................................................................................................................................................37 C.9 DBMS_OUTPUT............................................................................................................................37 C.9.1 The DISABLE procedure ................................................................................................37 C.9.2 The ENABLE procedure.................................................................................................37 C.9.3 The GET_LINE procedure ..............................................................................................37 C.9.4 The GET_LINES procedure...........................................................................................37 C.9.5 The NEW_LINE procedure............................................................................................37 C.9.6 The PUT procedure.........................................................................................................38 C.9.7 The PUT_LINE procedure..............................................................................................38.............................................................................................................................................................................39 C.10 DBMS_PIPE.................................................................................................................................39 C.10.1 The CREATE_PIPE function.......................................................................................39 C.10.2 The NEXT_ITEM_TYPE function...............................................................................39 C.10.3 The PACK_MESSAGE procedure...............................................................................40 C.10.4 The PURGE procedure.................................................................................................40 C.10.5 The RECEIVE_MESSAGE function ............................................................................40 C.10.6 The REMOVE_PIPE function......................................................................................40 C.10.7 The RESET_BUFFER procedure.................................................................................40 C.10.8 The SEND_MESSAGE function..................................................................................41 C.10.9 The UNIQUE_SESSION_NAME function..................................................................41 C.10.10 The UNPACK_MESSAGE procedure.......................................................................41.............................................................................................................................................................................42 C.11 DBMS_ROWID (PL/SQL8 Only)................................................................................................42 C.11.1 The ROWID_CREATE function..................................................................................42 C.11.2 The ROWID_INFO procedure ......................................................................................42 C.11.3 The ROWID_TYPE function ........................................................................................42 C.11.4 The ROWID_OBJECT function...................................................................................42 C.11.5 The ROWID_RELATIVE_FNO function....................................................................43 C.11.6 The ROWID_BLOCK_NUMBER function.................................................................43 ii

4. [Appendix A] Whats on the Companion Disk? Table of Contents C.11.7 The ROWID_ROW_NUMBER function.....................................................................43 C.11.8 The ROWID_TO_ABSOLUTE_FNO function...........................................................43 C.11.9 The ROWID_TO_EXTENDED function.....................................................................43 C.11.10 The ROWID_TO_RESTRICTED function................................................................43 C.11.11 The ROWID_VERIFY function.................................................................................43.............................................................................................................................................................................45 C.12 DBMS_SESSION.........................................................................................................................45 C.12.1 The CLOSE_DATABASE_LINK procedure...............................................................45 C.12.2 The IS_ROLE_ENABLED function .............................................................................45 C.12.3 The RESET_PACKAGE procedure.............................................................................45 C.12.4 The SET_LABEL procedure .........................................................................................45 C.12.5 The SET_NLS_LABEL procedure...............................................................................45 C.12.6 The SET_NLS procedure..............................................................................................45 C.12.7 The SET_ROLE procedure...........................................................................................46 C.12.8 The SET_SQL_TRACE procedure...............................................................................46 C.12.9 The UNIQUE_SESSION_ID function.........................................................................46.............................................................................................................................................................................47 C.13 DBMS_SNAPSHOT.....................................................................................................................47 C.13.1 The DROP_SNAPSHOT procedure.............................................................................47 C.13.2 The GET_LOG_AGE procedure..................................................................................47 C.13.3 The PURGE_LOG procedure.......................................................................................47 C.13.4 The REFRESH procedure.............................................................................................47 C.13.5 The REFRESH_ALL procedure...................................................................................48 C.13.6 The SET_UP procedure................................................................................................48 C.13.7 The WRAP_UP procedure............................................................................................48.............................................................................................................................................................................49 C.14 DBMS_SQL..................................................................................................................................49 C.14.1 The BIND_ARRAY procedure.....................................................................................49 C.14.2 The BIND_VARIABLE procedure ...............................................................................49 C.14.3 The CLOSE_CURSOR procedure................................................................................50 C.14.4 The COLUMN_VALUE procedure ..............................................................................50 C.14.5 The DEFINE_COLUMN procedure.............................................................................51 C.14.6 The EXECUTE function...............................................................................................51 C.14.7 The EXECUTE_AND_FETCH function ......................................................................52 C.14.8 The FETCH_ROWS function.......................................................................................52 C.14.9 The IS_OPEN function.................................................................................................52 C.14.10 The LAST_ERROR_POSITION function ..................................................................52 C.14.11 The LAST_ROW_COUNT function..........................................................................52 C.14.12 The LAST_ROW_ID function ....................................................................................52 C.14.13 The LAST_SQL_FUNCTION_CODE function .........................................................52 C.14.14 The OPEN_CURSOR function...................................................................................53 C.14.15 The PARSE procedure................................................................................................53 C.14.16 The VARIABLE_VALUE procedure.........................................................................53.............................................................................................................................................................................54 C.15 DBMS_TRANSACTION.............................................................................................................54 C.15.1 The ADVISE_COMMIT procedure.............................................................................54 C.15.2 The ADVISE_NOTHING procedure ............................................................................54 C.15.3 The ADVISE_ROLLBACK procedure........................................................................54 C.15.4 The COMMIT procedure..............................................................................................55 C.15.5 The COMMIT_COMMENT procedure ........................................................................55 C.15.6 The COMMIT_FORCE procedure...............................................................................55 C.15.7 The READ_ONLY procedure .......................................................................................55 iii

5. [Appendix A] Whats on the Companion Disk? Table of Contents C.15.8 The READ_WRITE procedure.....................................................................................55 C.15.9 The ROLLBACK procedure.........................................................................................56 C.15.10 The ROLLBACK_FORCE procedure........................................................................56 C.15.11 The ROLLBACK_SAVEPOINT procedure...............................................................56 C.15.12 The SAVEPOINT procedure......................................................................................56 C.15.13 The USE_ROLLBACK_SEGMENT procedure .........................................................56 C.15.14 The BEGIN_DISCRETE_TRANSACTION procedure.............................................56 C.15.15 The PURGE_MIXED procedure................................................................................57 C.15.16 The PURGE_LOST_DB procedure............................................................................57 C.15.17 The LOCAL_TRANSACTION_ID function.............................................................57 C.15.18 The STEP_ID function ................................................................................................57.............................................................................................................................................................................59 C.16 DBMS_UTILITY..........................................................................................................................59 C.16.1 The ANALYZE_SCHEMA procedure.........................................................................59 C.16.2 The COMMA_TO_TABLE procedure.........................................................................59 C.16.3 The COMPILE_SCHEMA procedure..........................................................................59 C.16.4 The FORMAT_CALL_STACK function.....................................................................59 C.16.5 The FORMAT_ERROR_STACK function..................................................................59 C.16.6 The GET_TIME function ..............................................................................................60 C.16.7 The IS_PARALLEL_SERVER function......................................................................60 C.16.8 The NAME_RESOLVE procedure...............................................................................60 C.16.9 The NAME_TOKENIZE procedure.............................................................................60 C.16.10 The PORT_STRING function .....................................................................................61 C.16.11 The TABLE_TO_COMMA procedure.......................................................................61.............................................................................................................................................................................62 C.17 UTL_FILE .....................................................................................................................................62 C.17.1 Setting Up UTL_FILE..................................................................................................62.............................................................................................................................................................................65 1. Introduction to PL/SQL...............................................................................................................................66 1.1 What Is PL/SQL?.............................................................................................................................66.............................................................................................................................................................................68 1.2 The Concept of Programming in Oracle Applications....................................................................68.............................................................................................................................................................................70 1.3 The Origins of PL/SQL ....................................................................................................................70 1.3.1 Improved Application Portability with PL/SQL ..............................................................70 1.3.2 Improved Execution Authority and Transaction Integrity with PL/SQL........................71.............................................................................................................................................................................72 1.4 PL/SQL Versions.............................................................................................................................72 1.4.1 Working with Multiple Versions of PL/SQL..................................................................72 1.4.2 How This Book Handles Different Versions of PL/SQL................................................73 1.4.3 PL/SQL Version 2.0........................................................................................................73 1.4.4 PL/SQL Release 2.1 .........................................................................................................80 1.4.5 PL/SQL Release 2.2 .........................................................................................................82 1.4.6 PL/SQL Release 2.3 .........................................................................................................83 1.4.7 PL/SQL Version 8.0........................................................................................................84 1.4.8 PL/SQL Release 1.1 .........................................................................................................86.............................................................................................................................................................................88 1.5 Advice for Oracle Programmers......................................................................................................88 1.5.1 Take a Creative, Even Radical Approach........................................................................88 1.5.2 Get Ready to Establish New Habits .................................................................................88 1.5.3 Assume that PL/SQL Has What You Need.....................................................................89 iv

6. [Appendix A] Whats on the Companion Disk? Table of Contents 1.5.4 Share Your Ideas ..............................................................................................................90.............................................................................................................................................................................91 1.6 A Few of My Favorite (PL/SQL) Things........................................................................................91 1.6.1 Anchored declarations.....................................................................................................91 1.6.2 Builtin functions............................................................................................................91 1.6.3 Builtin packages............................................................................................................91 1.6.4 The cursor FOR loop.......................................................................................................92 1.6.5 Scoping with nested blocks ..............................................................................................92 1.6.6 Module overloading.........................................................................................................92 1.6.7 Local modules..................................................................................................................93 1.6.8 Packages ...........................................................................................................................93.............................................................................................................................................................................95 1.7 Best Practices for PL/SQL Excellence............................................................................................95 1.7.1 Write as Little Code as Possible......................................................................................95 1.7.2 Synchronize Program and Data Structures......................................................................96 1.7.3 Center All Development Around Packages.....................................................................97 1.7.4 Standardize Your PL/SQL Development Environment..................................................98 . 1.7.5 Structured Code and Other Best Practices.......................................................................98...........................................................................................................................................................................101 2. PL/SQL Language Fundamentals.............................................................................................................102 2.1 The PL/SQL Character Set............................................................................................................102...........................................................................................................................................................................104 2.2 Identifiers.......................................................................................................................................104 2.2.1 Reserved Words.............................................................................................................105 2.2.2 Whitespace and Keywords .............................................................................................106...........................................................................................................................................................................107 2.3 Literals...........................................................................................................................................107 2.3.1 Embedding Single Quotes Inside a String.....................................................................107 2.3.2 Numeric Literals............................................................................................................108 2.3.3 Boolean Literals.............................................................................................................108...........................................................................................................................................................................110 2.4 The Semicolon Delimiter...............................................................................................................110...........................................................................................................................................................................111 2.5 Comments......................................................................................................................................111 2.5.1 SingleLine Comment Syntax.......................................................................................111 2.5.2 Multiline Comment Syntax ............................................................................................111...........................................................................................................................................................................113 2.6 The PRAGMA Keyword...............................................................................................................113...........................................................................................................................................................................114 2.7 Block Structure..............................................................................................................................114 2.7.1 Sections of the PL/SQL Block.......................................................................................114 2.7.2 Scope of a Block............................................................................................................115 2.7.3 Nested Blocks................................................................................................................115...........................................................................................................................................................................1173. Effective Coding Style.................................................................................................................................118 3.1 Fundamentals of Effective Layout.................................................................................................118 3.1.1 Revealing Logical Structure with Indentation...............................................................119 3.1.2 Using Case to Aid Readability .......................................................................................120 3.1.3 The UPPERlower Style...............................................................................................120 3.1.4 Formatting Single Statements........................................................................................121 v

7. [Appendix A] Whats on the Companion Disk? Table of Contents 3. Effective Coding Style 3.1.5 Formatting Your Declarations.......................................................................................122 3.1.6 Formatting Multiline Statements...................................................................................123...........................................................................................................................................................................126 3.2 Formatting SQL Statements ...........................................................................................................126...........................................................................................................................................................................129 3.3 Formatting Control Structures.......................................................................................................129 3.3.1 Formatting IF Statements ...............................................................................................129 3.3.2 Formatting Loops ...........................................................................................................130 3.3.3 Formatting Exception Handlers.....................................................................................131...........................................................................................................................................................................133 3.4 Formatting PL/SQL Blocks...........................................................................................................133...........................................................................................................................................................................135 3.5 Formatting Packages......................................................................................................................135...........................................................................................................................................................................137 3.6 Using Comments Effectively.........................................................................................................137 3.6.1 Comment As You Code.................................................................................................138 3.6.2 Explain the Why Not the How of Your Program............................................138 3.6.3 Make Comments Easy to Enter and Maintain...............................................................139 3.6.4 Maintain Indentation......................................................................................................140 3.6.5 Comment Declaration Statements.................................................................................141...........................................................................................................................................................................143 3.7 Documenting the Entire Package...................................................................................................143 3.7.1 Document the Package Specification............................................................................143 3.7.2 Document the Package Body.........................................................................................144...........................................................................................................................................................................146 4. Variables and Program Data.....................................................................................................................147 4.1 Identifiers.......................................................................................................................................147 4.1.1 Choose the Right Name.................................................................................................147 4.1.2 Select Readable Names ..................................................................................................148...........................................................................................................................................................................149 4.2 Scalar Datatypes .............................................................................................................................149 4.2.1 Numeric Datatypes........................................................................................................150 4.2.2 Numeric Subtypes..........................................................................................................152 4.2.3 Character Datatypes.......................................................................................................153 4.2.4 The Boolean Datatype...................................................................................................160 4.2.5 The DateTime Datatype..............................................................................................160 4.2.6 NLS Character Datatypes..............................................................................................161 4.2.7 LOB Datatypes..............................................................................................................162 4.2.8 Conversion Between Datatypes.....................................................................................166...........................................................................................................................................................................169 4.3 NULLs in PL/SQL.........................................................................................................................169 4.3.1 NULL Values in Comparisons......................................................................................170 4.3.2 Checking for NULL Values ...........................................................................................170 4.3.3 Function Results with NULL Arguments......................................................................171...........................................................................................................................................................................173 4.4 Variable Declarations .....................................................................................................................173 4.4.1 Constrained Declarations...............................................................................................173 4.4.2 Declaration Examples....................................................................................................173 4.4.3 Default Values...............................................................................................................174 4.4.4 NOT NULL Clause ........................................................................................................175 vi

8. [Appendix A] Whats on the Companion Disk? Table of Contents 4.5.1 Benefits of Anchored Declarations................................................................................176 4.5.2 Anchoring at Compile Time..........................................................................................176 4.5.3 Nesting Usages of the %TYPE Attribute......................................................................177 4.5.4 Anchoring to Variables in Other PL/SQL Blocks.........................................................178 4.5.5 Anchoring to NOT NULL Datatypes............................................................................179...........................................................................................................................................................................179 4.5 Anchored Declarations ...................................................................................................................179...........................................................................................................................................................................181 4.6 ProgrammerDefined Subtypes .....................................................................................................181 4.6.1 Declaring Subtypes........................................................................................................181 4.6.2 Examples of Subtype Declarations................................................................................182 4.6.3 Emulating Constrained Subtypes...................................................................................183...........................................................................................................................................................................185 4.7 Tips for Creating and Using Variables..........................................................................................185 4.7.1 Establish Clear Variable Naming Conventions.............................................................185 4.7.2 Name Subtypes to SelfDocument Code......................................................................187 4.7.3 Avoid Recycling Variables............................................................................................188 4.7.4 Use Named Constants to Avoid Hardcoding Values.....................................................188 4.7.5 Convert Variables into Named Constants ......................................................................189 4.7.6 Remove Unused Variables from Programs...................................................................190 4.7.7 Use %TYPE When a Variable Represents a Column ....................................................190 4.7.8 Use %TYPE to Standardize Nondatabase Declarations................................................191 4.7.9 Use Variables to Hide Complex Logic..........................................................................192...........................................................................................................................................................................196 5. Conditional and Sequential Control.........................................................................................................197 . 5.1 Conditional Control Statements.....................................................................................................197 5.1.1 The IFTHEN Combination..........................................................................................197 5.1.2 The IFTHENELSE Combination..............................................................................198 5.1.3 The IFELSIF Combination..........................................................................................199 5.1.4 Nested IF Statements.....................................................................................................203...........................................................................................................................................................................205 5.2 Sequential Control Statements.......................................................................................................205 5.2.1 The GOTO Statement....................................................................................................205 5.2.2 The NULL Statement....................................................................................................208 ............................................................................................................................................................................211 6. Database Interaction and Cursors............................................................................................................212 6.1 Transaction Management...............................................................................................................212 6.1.1 The COMMIT Statement...............................................................................................213 6.1.2 The ROLLBACK Statement .........................................................................................213 . 6.1.3 The SAVEPOINT Statement.........................................................................................214 6.1.4 The SET TRANSACTION Statement...........................................................................214 6.1.5 The LOCK TABLE Statement......................................................................................215...........................................................................................................................................................................217 6.2 Cursors in PL/SQL .........................................................................................................................217 6.2.1 Types of Cursors............................................................................................................218 6.2.2 Cursor Operations..........................................................................................................218...........................................................................................................................................................................220 6.3 Implicit and Explicit Cursors.........................................................................................................220 6.3.1 Implicit Cursors.............................................................................................................220 6.3.2 Drawbacks of Implicit Cursors......................................................................................220 vii

9. [Appendix A] Whats on the Companion Disk? Table of Contents 6.3.3 Explicit Cursors.............................................................................................................222...........................................................................................................................................................................224 6.4 Declaring Cursors..........................................................................................................................224 6.4.1 The Cursor Name...........................................................................................................224 6.4.2 PL/SQL Variables in a Cursor.......................................................................................225 6.4.3 Identifier Precedence in a Cursor..................................................................................225 . 6.4.4 The Cursor RETURN Clause........................................................................................226...........................................................................................................................................................................229 6.5 Opening Cursors............................................................................................................................229...........................................................................................................................................................................231 6.6 Fetching from Cursors...................................................................................................................231 6.6.1 Matching Column List with INTO Clause....................................................................231 6.6.2 Fetching Past the Last Row...........................................................................................233...........................................................................................................................................................................234 6.7 Column Aliases in Cursors............................................................................................................234...........................................................................................................................................................................236 6.8 Closing Cursors ..............................................................................................................................236 6.8.1 Maximum Number of Cursors.......................................................................................236 6.8.2 Closing Local Cursors...................................................................................................237...........................................................................................................................................................................238 6.9 Cursor Attributes ............................................................................................................................238 6.9.1 The %FOUND Attribute ................................................................................................239 6.9.2 The %NOTFOUND Attribute.......................................................................................240 6.9.3 The %ROWCOUNT Attribute......................................................................................240 6.9.4 The %ISOPEN Attribute...............................................................................................241 6.9.5 Implicit SQL Cursor Attributes.....................................................................................241 6.9.6 Differences Between Implicit and Explicit Cursor Attributes.......................................241...........................................................................................................................................................................243 6.10 Cursor Parameters........................................................................................................................243 6.10.1 Generalizing Cursors with Parameters........................................................................244 6.10.2 Opening Cursors with Parameters...............................................................................244 6.10.3 Scope of Cursor Parameters .........................................................................................245 6.10.4 Cursor Parameter Modes.............................................................................................245 6.10.5 Default Values for Parameters.....................................................................................245...........................................................................................................................................................................246 6.11 SELECT FOR UPDATE in Cursors............................................................................................246 6.11.1 Releasing Locks with COMMIT.................................................................................247 6.11.2 The WHERE CURRENT OF Clause..........................................................................248 6.12.1 Features of Cursor Variables.......................................................................................250 6.12.2 Similarities to Static Cursors.......................................................................................250 6.12.3 Declaring REF CURSOR Types and Cursor Variables ...............................................251 6.12.4 Opening Cursor Variables...........................................................................................252 6.12.5 Fetching from Cursor Variables..................................................................................253 6.12.6 Rules for Cursor Variables..........................................................................................254 6.12.7 Passing Cursor Variables as Arguments......................................................................255 6.12.8 Cursor Variable Restrictions ........................................................................................257...........................................................................................................................................................................260 6.12 Cursor Variables..........................................................................................................................262...........................................................................................................................................................................264 6.13 Working with Cursors..................................................................................................................264 6.13.1 Validating Foreign Key Entry with Cursors................................................................264 6.13.2 Managing a Work Queue with SELECT FOR UPDATE ............................................266 viii...........................................................................................................................................................................270

10. [Appendix A] Whats on the Companion Disk? Table of Contents 7. Loops............................................................................................................................................................271 7.1 Loop Basics ....................................................................................................................................271 7.1.1 Examples of Different Loops .........................................................................................271 7.1.2 Structure of PL/SQL Loops...........................................................................................272...........................................................................................................................................................................274 7.2 The Simple Loop...........................................................................................................................274 7.2.1 Terminating a Simple Loop: EXIT and EXIT WHEN..................................................275 7.2.2 Emulating a REPEAT UNTIL Loop.............................................................................276...........................................................................................................................................................................277 7.3 The Numeric FOR Loop................................................................................................................277 7.3.1 Rules for Numeric FOR Loops......................................................................................277 7.3.2 Examples of Numeric FOR Loops .................................................................................278 7.3.3 Handling Nontrivial Increments....................................................................................279...........................................................................................................................................................................280 7.4 The Cursor FOR Loop...................................................................................................................280 7.4.1 Example of Cursor FOR Loops.....................................................................................280 7.4.2 The Cursor FOR Loop Record .......................................................................................281 7.4.3 When to Use the Cursor FOR Loop ...............................................................................282...........................................................................................................................................................................284 7.5 The WHILE Loop..........................................................................................................................284 7.5.1 The Infinite WHILE Loop.............................................................................................285...........................................................................................................................................................................286 7.6 Managing Loop Execution .............................................................................................................286 7.6.1 Loop Labels...................................................................................................................286 7.6.2 Loop Scope....................................................................................................................288...........................................................................................................................................................................290 7.7 Tips for PL/SQL Loops.................................................................................................................290 7.7.1 Naming Loop Indexes ....................................................................................................290 7.7.2 The Proper Way to Say Goodbye..................................................................................291 7.7.3 Avoiding the Phony Loop..............................................................................................293 7.7.4 PL/SQL Loops Versus SQL Processing........................................................................293 8.1 Why Exception Handling?.............................................................................................................296...........................................................................................................................................................................297 8. Exception Handlers .....................................................................................................................................298...........................................................................................................................................................................300 8.2 The Exception Section...................................................................................................................300...........................................................................................................................................................................302 8.3 Types of Exceptions .......................................................................................................................302 8.3.1 Named System Exceptions............................................................................................302 8.3.2 Named ProgrammerDefined Exceptions.....................................................................304 8.3.3 Unnamed System Exceptions........................................................................................305 8.3.4 Unnamed ProgrammerDefined Exceptions.................................................................306...........................................................................................................................................................................308 8.4 Determining ExceptionHandling Behavior.................................................................................308 8.4.1 Scope of an Exception...................................................................................................308 8.4.2 Propagation of an Exception..........................................................................................312...........................................................................................................................................................................315 8.5 Raising an Exception.....................................................................................................................315 8.5.1 Who Raises the Exception?...........................................................................................315 8.5.2 ReRaising an Exception..............................................................................................316 8.5.3 Exceptions Raised in a Declaration...............................................................................317 ix

11. [Appendix A] Whats on the Companion Disk? Table of Contents 8.5.4 Exceptions Raised in an Exception Handler..................................................................317...........................................................................................................................................................................320 8.6 Handling Exceptions......................................................................................................................320 8.6.1 Combining Multiple Exceptions in a Single Handler....................................................320 8.6.2 Unhandled Exceptions...................................................................................................321 8.6.3 Using SQLCODE and SQLERRM in WHEN OTHERS Clause..................................321 8.6.4 Continuing Past Exceptions...........................................................................................322...........................................................................................................................................................................325 8.7 ClientServer Error Communication.............................................................................................325 8.7.1 Using RAISE_APPLICATION_ERROR......................................................................325 8.7.2 RAISE_APPLICATION_ERROR in a database trigger...............................................325...........................................................................................................................................................................327 8.8 NO_DATA_FOUND: Multipurpose Exception............................................................................327...........................................................................................................................................................................329 8.9 Exception Handler as IF Statement...............................................................................................329 ............................................................................................................................................................................331 8.10 RAISE Nothing but Exceptions...................................................................................................331...........................................................................................................................................................................334 9. Records in PL/SQL.....................................................................................................................................335 9.1 Record Basics .................................................................................................................................335 9.1.1 Different Types of Records ............................................................................................335 9.1.2 Accessing RecordBased Data......................................................................................336 9.1.3 Benefits of Using Records.............................................................................................336 9.1.4 Guidelines for Using Records........................................................................................337 9.1.5 Referencing a Record and its Fields..............................................................................338 9.1.6 Comparing Two Records...............................................................................................338...........................................................................................................................................................................340 9.2 TableBased Records....................................................................................................................340 9.2.1 Declaring Records with the %ROWTYPE Attribute....................................................340...........................................................................................................................................................................342 9.3 CursorBased Records..................................................................................................................342 9.3.1 Choosing Columns for a Cursor Record........................................................................342 9.3.2 Setting the Records Column Names.............................................................................343...........................................................................................................................................................................345 9.4 ProgrammerDefined Records......................................................................................................345 9.4.1 Declaring ProgrammerDefined Record TYPEs..........................................................345 9.4.2 Declaring the Record.....................................................................................................346 9.4.3 Examples of ProgrammerDefined Record Declarations.............................................347...........................................................................................................................................................................349 9.5 Assigning Values to and from Records.........................................................................................349 9.5.1 Direct Field Assignment................................................................................................349 9.5.2 SELECT INTO from an Implicit Cursor.......................................................................350 9.5.3 FETCH INTO from an Explicit Cursor.........................................................................350 9.5.4 Aggregate Assignment ..................................................................................................351 ............................................................................................................................................................................352 9.6 Record Types and Record Compatibility .......................................................................................352 9.6.1 Assignment Restrictions................................................................................................353 9.6.2 Record Initialization......................................................................................................353...........................................................................................................................................................................355x

12. [Appendix A] Whats on the Companion Disk? Table of Contents 9.7 Nested Records..............................................................................................................................355 9.7.1 Example of Nested Records ...........................................................................................355 9.7.2 Dot Notation with Nested Records................................................................................356 9.7.3 Aggregate Assignments of Nested Records ...................................................................356 9.7.4 Denormalizing Program Data with Nested Records......................................................357 10.1 PL/SQL Tables and Other Collections........................................................................................360 10.1.1 PL/SQL Tables............................................................................................................361 10.1.2 Nested Tables and VARRAYs....................................................................................362...........................................................................................................................................................................362 10. PL/SQL Tables..........................................................................................................................................362...........................................................................................................................................................................363 10.2 Characteristics of PL/SQL Tables...............................................................................................363...........................................................................................................................................................................365 10.3 PL/SQL Tables and DML Statements.........................................................................................365...........................................................................................................................................................................366 10.4 Declaring a PL/SQL Table ...........................................................................................................366 10.4.1 Defining the Table TYPE............................................................................................366 10.4.2 Declaring the PL/SQL Table.......................................................................................367...........................................................................................................................................................................368 10.5 Referencing and Modifying PL/SQL Table Rows .......................................................................368 10.5.1 Automatic Conversion of Row Number Expressions..................................................368 10.5.2 Referencing an Undefined Row ...................................................................................368 10.5.3 Nonsequential Use of PL/SQL Table..........................................................................369 10.5.4 Passing PL/SQL Tables as Parameters........................................................................370...........................................................................................................................................................................372 10.6 Filling the Rows of a PL/SQL Table...........................................................................................372 10.6.1 Direct Assignment.......................................................................................................372 10.6.2 Iterative Assignment....................................................................................................372 10.6.3 Aggregate Assignment ................................................................................................373 ............................................................................................................................................................................374 10.7 Clearing the PL/SQL Table.........................................................................................................374...........................................................................................................................................................................376 10.8 PL/SQL Table Enhancements in PL/SQL Release 2.3................................................................376 10.8.1 PL/SQL Tables of Records..........................................................................................377 10.8.2 PL/SQL Table Builtins..............................................................................................379........

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