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Writing Control Writing Control StructuresStructures

Part DPart D

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PL/SQL Decision Control PL/SQL Decision Control StructuresStructures

Sequential processing Sequential processing Processes statements one after anotherProcesses statements one after another

Decision control structures Decision control structures Alter order in which statements executeAlter order in which statements execute Based on values of certain variablesBased on values of certain variables

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Controlling PL/SQL Flow Controlling PL/SQL Flow of Executionof Execution

Controlling PL/SQL Flow Controlling PL/SQL Flow of Executionof Execution

You can change the logical You can change the logical flow of statements using flow of statements using conditional IF statements and conditional IF statements and loop control structures. loop control structures.

Conditional IFConditional IF statements:statements: IF-THEN-END IFIF-THEN-END IF IF-THEN-ELSE-END IFIF-THEN-ELSE-END IF IF-THEN-ELSIF-END IFIF-THEN-ELSIF-END IF

You can change the logical You can change the logical flow of statements using flow of statements using conditional IF statements and conditional IF statements and loop control structures. loop control structures.

Conditional IFConditional IF statements:statements: IF-THEN-END IFIF-THEN-END IF IF-THEN-ELSE-END IFIF-THEN-ELSE-END IF IF-THEN-ELSIF-END IFIF-THEN-ELSIF-END IF

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IF StatementsIF StatementsIF StatementsIF Statements

IF condition THEN statements;[ELSIF condition THEN statements;][ELSE statements;]END IF;

IF condition THEN statements;[ELSIF condition THEN statements;][ELSE statements;]END IF;

SyntaxSyntax

Simple IF statement:Simple IF statement:

Set the manager ID to 22 if the employee Set the manager ID to 22 if the employee name is Osborne.name is Osborne.

SyntaxSyntax

Simple IF statement:Simple IF statement:

Set the manager ID to 22 if the employee Set the manager ID to 22 if the employee name is Osborne.name is Osborne.IF v_ename = 'OSBORNE' THEN v_mgr := 22;END IF;

IF v_ename = 'OSBORNE' THEN v_mgr := 22;END IF;

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PL/SQL Comparison PL/SQL Comparison OperatorsOperators

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Simple IF StatementsSimple IF StatementsSimple IF StatementsSimple IF Statements

Set the job title to Salesman, the department number to 35, and the Set the job title to Salesman, the department number to 35, and the commission to 20% of the current salary if the last name is Miller.commission to 20% of the current salary if the last name is Miller.

ExampleExample

Set the job title to Salesman, the department number to 35, and the Set the job title to Salesman, the department number to 35, and the commission to 20% of the current salary if the last name is Miller.commission to 20% of the current salary if the last name is Miller.

ExampleExample

. . .IF v_ename = 'MILLER' THEN v_job := 'SALESMAN'; v_deptno := 35; v_new_comm := sal * 0.20; END IF;. . .

. . .IF v_ename = 'MILLER' THEN v_job := 'SALESMAN'; v_deptno := 35; v_new_comm := sal * 0.20; END IF;. . .

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IF-THEN-ELSE IF-THEN-ELSE Statement Execution Statement Execution

FlowFlow

IF-THEN-ELSE IF-THEN-ELSE Statement Execution Statement Execution

FlowFlowIF conditionIF condition

TRUETRUE

THEN actionsTHEN actions(including further IFs)(including further IFs)

THEN actionsTHEN actions(including further IFs)(including further IFs)

FALSEFALSE

ELSE actionsELSE actions(including further IFs)(including further IFs)

ELSE actionsELSE actions(including further IFs)(including further IFs)

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IF-THEN-ELSE IF-THEN-ELSE StatementsStatements

IF-THEN-ELSE IF-THEN-ELSE StatementsStatements

Set a flag for orders where there Set a flag for orders where there are fewer than five days are fewer than five days between order date and ship between order date and ship date.date.

ExampleExample

Set a flag for orders where there Set a flag for orders where there are fewer than five days are fewer than five days between order date and ship between order date and ship date.date.

ExampleExample...IF v_shipdate - v_orderdate < 5 THEN v_ship_flag := 'Acceptable';ELSE v_ship_flag := 'Unacceptable';END IF;...

...IF v_shipdate - v_orderdate < 5 THEN v_ship_flag := 'Acceptable';ELSE v_ship_flag := 'Unacceptable';END IF;...

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IF-THEN-ELSIF IF-THEN-ELSIF Statement Execution Statement Execution

FlowFlow

IF-THEN-ELSIF IF-THEN-ELSIF Statement Execution Statement Execution

FlowFlowIF conditionIF condition

TRUETRUE

THEN actionsTHEN actionsTHEN actionsTHEN actions

FALSEFALSE

ELSIFELSIFconditioncondition

ELSIFELSIFconditioncondition

TRUETRUE

THEN actionsTHEN actionsTHEN actionsTHEN actions

FALSEFALSE

ELSEELSEactionsactionsELSEELSE

actionsactions

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IF-THEN-ELSIF IF-THEN-ELSIF StatementsStatements

IF-THEN-ELSIF IF-THEN-ELSIF StatementsStatements

For a given value, calculate a For a given value, calculate a percentage of that value based percentage of that value based on a condition.on a condition.

ExampleExample

For a given value, calculate a For a given value, calculate a percentage of that value based percentage of that value based on a condition.on a condition.

ExampleExample. . .IF v_start > 100 THEN v_start := 2 * v_start;ELSIF v_start >= 50 THEN v_start := .5 * v_start;ELSE v_start := .1 * v_start;END IF;. . .

. . .IF v_start > 100 THEN v_start := 2 * v_start;ELSIF v_start >= 50 THEN v_start := .5 * v_start;ELSE v_start := .1 * v_start;END IF;. . .

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Building Logical Building Logical ConditionsConditions

Building Logical Building Logical ConditionsConditions

You can handle null values with the You can handle null values with the IS NULL operator.IS NULL operator.

Any arithmetic expression Any arithmetic expression containing a null value evaluates to containing a null value evaluates to NULL.NULL.

Concatenated expressions with null Concatenated expressions with null values treat null values as an values treat null values as an empty string.empty string.

NULL acts as FalseNULL acts as False The IS NULL condition evaluates to The IS NULL condition evaluates to

TRUE only if the variable it is TRUE only if the variable it is checking is NULL.checking is NULL.

You can handle null values with the You can handle null values with the IS NULL operator.IS NULL operator.

Any arithmetic expression Any arithmetic expression containing a null value evaluates to containing a null value evaluates to NULL.NULL.

Concatenated expressions with null Concatenated expressions with null values treat null values as an values treat null values as an empty string.empty string.

NULL acts as FalseNULL acts as False The IS NULL condition evaluates to The IS NULL condition evaluates to

TRUE only if the variable it is TRUE only if the variable it is checking is NULL.checking is NULL.

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Logic TablesLogic TablesLogic TablesLogic Tables

Build a simple Boolean condition Build a simple Boolean condition with a comparison operator.with a comparison operator.

Build a simple Boolean condition Build a simple Boolean condition with a comparison operator.with a comparison operator.

NOT

TRUE

FALSE

NULL

OR

TRUE

FALSE

NULL

TRUE FALSE NULL

FALSE

TRUE

NULL

AND

TRUE

FALSE

NULL

TRUE FALSE NULL

TRUE

NULL NULL

NULL

FALSE FALSE

FALSE

FALSE

FALSE

TRUE

TRUE

TRUE

TRUETRUE

FALSE

NULL NULL

NULL

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Boolean ConditionsBoolean ConditionsBoolean ConditionsBoolean Conditions

What is the value of V_FLAG in What is the value of V_FLAG in each case?each case?

What is the value of V_FLAG in What is the value of V_FLAG in each case?each case?

V_REORDER_FLAG V_AVAILABLE_FLAG V_FLAG

TRUE TRUE

TRUE FALSE

NULL TRUE

NULL FALSE

v_flag := v_reorder_flag AND v_available_flag; v_flag := v_reorder_flag AND v_available_flag;

TRUETRUE

FALSEFALSE

NULLNULL

FALSEFALSE

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Evaluating AND and OR Evaluating AND and OR in an Expressionin an Expression

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LoopsLoops

Systematically executes program Systematically executes program statementsstatements

Periodically evaluates exit condition to Periodically evaluates exit condition to determine if loop should repeat or exitdetermine if loop should repeat or exit

Pretest loopPretest loop Evaluates exit condition before any program Evaluates exit condition before any program

commands executecommands execute Posttest loop Posttest loop

Executes program commands before loop Executes program commands before loop evaluates exit condition for first timeevaluates exit condition for first time

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Iterative Control: LOOP Iterative Control: LOOP StatementsStatements

Iterative Control: LOOP Iterative Control: LOOP StatementsStatements

Loops repeat a statement or Loops repeat a statement or sequence of statements multiple sequence of statements multiple times.times.

There are three loop types:There are three loop types: Basic loopBasic loop FOR loopFOR loop WHILE loopWHILE loop

Loops repeat a statement or Loops repeat a statement or sequence of statements multiple sequence of statements multiple times.times.

There are three loop types:There are three loop types: Basic loopBasic loop FOR loopFOR loop WHILE loopWHILE loop

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Basic LoopBasic LoopBasic LoopBasic Loop

SyntaxSyntax SyntaxSyntaxLOOP statement1; . . . EXIT [WHEN condition];END LOOP;

LOOP statement1; . . . EXIT [WHEN condition];END LOOP;

where: condition is a Boolean variable or expression (TRUE, FALSE, or NULL);

where: condition is a Boolean variable or expression (TRUE, FALSE, or NULL);

-- delimiter-- delimiter

-- statements-- statements

-- EXIT statement-- EXIT statement

-- delimiter-- delimiter

•A basic loop can contain multiple EXIT statements.•A basic loop can contain multiple EXIT statements.

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Basic LoopBasic LoopBasic LoopBasic Loop

DECLARE v_ordid item.ordid%TYPE := 601; v_counter NUMBER(2) := 1;BEGIN LOOP INSERT INTO item(ordid, itemid) VALUES(v_ordid, v_counter); v_counter := v_counter + 1; EXIT WHEN v_counter > 10; END LOOP;END;

DECLARE v_ordid item.ordid%TYPE := 601; v_counter NUMBER(2) := 1;BEGIN LOOP INSERT INTO item(ordid, itemid) VALUES(v_ordid, v_counter); v_counter := v_counter + 1; EXIT WHEN v_counter > 10; END LOOP;END;

ExampleExample ExampleExample

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FOR LoopFOR LoopFOR LoopFOR Loop SyntaxSyntax

Use a FOR loop to shortcut the test Use a FOR loop to shortcut the test for the number of iterations.for the number of iterations.

Do not declare the counter; it is Do not declare the counter; it is declared implicitly.declared implicitly.

The lower bound and upper bound The lower bound and upper bound of the loop range can be literals, of the loop range can be literals, variables, or expressions, variables, or expressions, but must but must evaluate to integersevaluate to integers

SyntaxSyntax

Use a FOR loop to shortcut the test Use a FOR loop to shortcut the test for the number of iterations.for the number of iterations.

Do not declare the counter; it is Do not declare the counter; it is declared implicitly.declared implicitly.

The lower bound and upper bound The lower bound and upper bound of the loop range can be literals, of the loop range can be literals, variables, or expressions, variables, or expressions, but must but must evaluate to integersevaluate to integers

FOR counter in [REVERSE] lower_bound..upper_bound LOOP statement1; statement2; . . .END LOOP;

FOR counter in [REVERSE] lower_bound..upper_bound LOOP statement1; statement2; . . .END LOOP;

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FOR LoopFOR LoopFOR LoopFOR Loop GuidelinesGuidelines

Reference the counter within the Reference the counter within the loop only; it is undefined outside the loop only; it is undefined outside the loop.loop.

The lower and upper bounds of the The lower and upper bounds of the loop could be values, variables, or loop could be values, variables, or expressionsexpressions

Do Do notnot reference the counter as the reference the counter as the target of an assignment. An error target of an assignment. An error message rises if you do so.message rises if you do so.

GuidelinesGuidelines Reference the counter within the Reference the counter within the

loop only; it is undefined outside the loop only; it is undefined outside the loop.loop.

The lower and upper bounds of the The lower and upper bounds of the loop could be values, variables, or loop could be values, variables, or expressionsexpressions

Do Do notnot reference the counter as the reference the counter as the target of an assignment. An error target of an assignment. An error message rises if you do so.message rises if you do so.

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FOR LoopFOR LoopFOR LoopFOR Loop Insert the first 10 new line items Insert the first 10 new line items

for order number 601.for order number 601. ExampleExample

Insert the first 10 new line items Insert the first 10 new line items for order number 601.for order number 601.

ExampleExample

DECLARE v_ordid item.ordid%TYPE := 601;BEGIN FOR i IN 1..10 LOOP INSERT INTO item(ordid, itemid) VALUES(v_ordid, i); END LOOP;END;

DECLARE v_ordid item.ordid%TYPE := 601;BEGIN FOR i IN 1..10 LOOP INSERT INTO item(ordid, itemid) VALUES(v_ordid, i); END LOOP;END;

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WHILE LoopWHILE LoopWHILE LoopWHILE Loop

SyntaxSyntax

Use the WHILE loop to Use the WHILE loop to repeat statements while a repeat statements while a condition is TRUE.condition is TRUE.

SyntaxSyntax

Use the WHILE loop to Use the WHILE loop to repeat statements while a repeat statements while a condition is TRUE.condition is TRUE.

WHILE condition LOOP statement1; statement2; . . .END LOOP;

WHILE condition LOOP statement1; statement2; . . .END LOOP;

Condition isCondition isevaluated at the evaluated at the beginning ofbeginning ofeach iteration.each iteration.

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WHILE LoopWHILE LoopWHILE LoopWHILE Loop ExampleExample ExampleExample

SQL>ACCEPT v_dept_name PROMPT 'Enter the dept. name: 'SQL>ACCEPT num_depts PROMPT 'Enter number of depts: ' SQL>DECLAREv_count NUMBER(2) := 1;BEGIN WHILE v_count <= &num_depts LOOP INSERT INTO dept(deptno,dname) VALUES (v_count, &v_dept_name); v_count := v_count + 1; END LOOP; COMMIT;END;/

SQL>ACCEPT v_dept_name PROMPT 'Enter the dept. name: 'SQL>ACCEPT num_depts PROMPT 'Enter number of depts: ' SQL>DECLAREv_count NUMBER(2) := 1;BEGIN WHILE v_count <= &num_depts LOOP INSERT INTO dept(deptno,dname) VALUES (v_count, &v_dept_name); v_count := v_count + 1; END LOOP; COMMIT;END;/

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Working with Working with Composite Composite DatatypesDatatypes

Working with Working with Composite Composite DatatypesDatatypes

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The %ROWTYPE The %ROWTYPE AttributeAttribute

The %ROWTYPE The %ROWTYPE AttributeAttribute

Declare a variable according to a Declare a variable according to a collection of columns in a database collection of columns in a database table or view.table or view.

Prefix %ROWTYPE with the Prefix %ROWTYPE with the database table.database table.

Fields in the record take their Fields in the record take their names and datatypes from the names and datatypes from the columns of the table or view.columns of the table or view.

Declare a variable according to a Declare a variable according to a collection of columns in a database collection of columns in a database table or view.table or view.

Prefix %ROWTYPE with the Prefix %ROWTYPE with the database table.database table.

Fields in the record take their Fields in the record take their names and datatypes from the names and datatypes from the columns of the table or view.columns of the table or view.

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The %ROWTYPE The %ROWTYPE AttributeAttribute

The %ROWTYPE The %ROWTYPE AttributeAttribute

ExamplesExamples Declare a variable to store the Declare a variable to store the

same information about a same information about a department as it is stored in the department as it is stored in the DEPT table. DEPT table.

Declare a variable to store the Declare a variable to store the same information about an same information about an employee as it is stored in the employee as it is stored in the EMP table.EMP table.

ExamplesExamples Declare a variable to store the Declare a variable to store the

same information about a same information about a department as it is stored in the department as it is stored in the DEPT table. DEPT table.

Declare a variable to store the Declare a variable to store the same information about an same information about an employee as it is stored in the employee as it is stored in the EMP table.EMP table.

dept_record dept%ROWTYPE; dept_record dept%ROWTYPE;

emp_record emp%ROWTYPE; emp_record emp%ROWTYPE;

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%ROWTYPE Example%ROWTYPE Example

SQL> SET SERVEROUTPUT ON;SQL> SET SERVEROUTPUT ON;SQL> DECLARESQL> DECLARE d dept%ROWTYPE;d dept%ROWTYPE; BEGINBEGIN SELECT deptno,dname,loc INTO d SELECT deptno,dname,loc INTO d

FROM dept WHERE deptno=10;FROM dept WHERE deptno=10; DBMS_OUTPUT.PUT_LINE(d.dname);DBMS_OUTPUT.PUT_LINE(d.dname); END;END; //ACCOUNTINGACCOUNTING