C20.0046: Database Management Systems Lecture #19

M.P. Johnson, DBMS, Stern/NYU, Sp2004

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C20.0046: Database Management SystemsLecture #19

Matthew P. Johnson

Stern School of Business, NYU

Spring, 2004


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Agenda Previously: JDBC Next: Project part 3 due now Project part 4 due next week Scripting for SQL

SPs Scripting for SQL on the web

CGI/Perl PHP

Security


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Recap: JDBC

Host language + Embedded SQL

Preprocessor

Host Language + function calls

Host language compiler

Executable

Preprocessor

Host language compiler

Oracle’sPro*C

javac + jar

prog.pc

Prog.java

Proj.class


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Java & parameter-based SQL Like SQL/CLI in C, Java also supports

parameterized queries (why?)

1. Prepare structure of query

2. Then can set values

PreparedStatement ps = conn.prepareStatement( "SELECT * FROM table WHERE f1 = ? and f2 = ?");ps.setString(1 “abc");ps.setString(2, “def");ResultSet rs = ps.executeQuery();...

PreparedStatement ps = conn.prepareStatement( "SELECT * FROM table WHERE f1 = ? and f2 = ?");ps.setString(1 “abc");ps.setString(2, “def");ResultSet rs = ps.executeQuery();...


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Also: ODBC Used by Microsoft platforms/tools, others

Access: Start | Control Panel | Administrative Tools | Data

Sources (ODBC)

Similar to JDBC

Won’t cover


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Other combinations So far: C/Pro*C, Java/JDBC Q: Only choices? A: No “Call-level interface” for C: SQL/CLI

ODBC Embedded Java: SQL/J CLI for Perl, PHP, etc. Stored Procedures (next) {langs} x {dyn/not} x {SPs/not} x {DBMSs}


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Step back Recall basic problem: need SQL plus

stronger programming lang need to connect the two langs

In all these case (and web apps next time): put SQL in (traditional lang) programs

Another way: let programs in SQL i.e., put programs in the DBMS “stored procedures”


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Next topic: SPs (8.2) “Persistent, Stored Modules” / “Stored Procedures /

“PL/SQL programs” (in Oracle) Added to MySQL in 5.0

Another way to connect application programming language and SQL

Supports usual things: Declare, set vars to vals of expressions Print output Define (optional) procedures, functions Cursors

PL/SQL can compute n!


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PL/SQL “Procedural Language/SQL”

Oracle’s language for stored procedures Simple, interpreted, procedural language

But Pascal-like: BEGIN END, not { } AND OR, not && || vars defined at top of procedre how return works


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PL/SQL Generally speaking can be used wherever

SQL can be sqlplus embeded SQL

Can store programs in files (.sql), run later @myprog.sql runs code in myprog.sql


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Scripting languages Big problems v. small problems Big solutions v. small solutions

Programming languages: C/C++, Java, etc.

Scripting languages: PL/SQL, Perl, PHP, Unix shell, DOS batch files, Python,

Excel macros, VBA, JavaScript Usual properties of scripting languages:

Interpreted Don’t require functions/procedures Weakly typed


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PL/SQL Structure of procedure body:

As in Pascal, var declars precede body

DECLARE --Optional--var declarations

BEGIN--executable statements

--queries/updates, etc.

END;

/ --to execute

DECLARE --Optional--var declarations

BEGIN--executable statements

--queries/updates, etc.

END;

/ --to execute


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PL/SQL: Hello, World http://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/hello.sql

SET SERVEROUTPUT ON;

BEGIN

-- print out message

DBMS_OUTPUT.PUT_LINE('Hello World, from PL/SQL');

END;

/

SET SERVEROUTPUT ON;

BEGIN

-- print out message

DBMS_OUTPUT.PUT_LINE('Hello World, from PL/SQL');

END;

/


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PL/SQL code examples One example:

Likes(drinker, beverage)

Another example: http://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/age.sql

BEGIN

INSERT INTO Likes VALUES(‘Izzy', ‘milk');

DELETE FROM Likes

WHERE drinker = ‘Izzy' AND

beverage = ‘Beaujolais Nouveau ';

COMMIT;

END; /

BEGIN

INSERT INTO Likes VALUES(‘Izzy', ‘milk');

DELETE FROM Likes

WHERE drinker = ‘Izzy' AND

beverage = ‘Beaujolais Nouveau ';

COMMIT;

END; /


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Procedures Stored database objects that use a PL/SQL

statement(s) in their body Create/drop similar to other SQL objects:

ALTER PROCEDURE… in MySQL

CREATE PROCEDURE <my-proc> (<params>)

<procedure body as above>;

CREATE PROCEDURE <my-proc> (<params>)

<procedure body as above>;

DROP PROCEDURE <my-proc>;DROP PROCEDURE <my-proc>;

CREATE OR REPLACE PROCEDURE <my-proc>(<params>)<procedure body as above>;

CREATE OR REPLACE PROCEDURE <my-proc>(<params>)<procedure body as above>;


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Example procedure Define the procedure:

Now we can call it:

CREATE PROCEDURE testProcedureBEGIN

INSERT INTO Student VALUES (5, ‘Joe’);COMMIT;

END;

CREATE PROCEDURE testProcedureBEGIN

INSERT INTO Student VALUES (5, ‘Joe’);COMMIT;

END;

EXEC testProcedure;EXEC testProcedure;


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More details on procedures Parameter list has name-mode-type triples: Modes: IN, OUT, or IN OUT

Fulfills role similar to pass-by-value v. pass-by-reference

Default is IN

Types must match, so can get exact field type:

relation.attribute%TYPErelation.attribute%TYPE


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Procedure example A procedure to take a beer and price and add

it to Joe's menu: Sells(bar, beer, price)

CREATE PROCEDURE joeMenu(b IN Sells.beer%TYPE,p IN Sells.price%TYPE) AS

BEGININSERT INTO SellsVALUES('Joe''s Bar', b, p);

END;/

CREATE PROCEDURE joeMenu(b IN Sells.beer%TYPE,p IN Sells.price%TYPE) AS

BEGININSERT INTO SellsVALUES('Joe''s Bar', b, p);

END;/


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Branching IF–THEN statements use THEN Must end with END IF Use ELSIF in place of ELSE IF

Example: http://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/maxval.sql

IF <condition> THEN

<statement(s)>

ELSIF

<statement(s)>

END IF;

IF <condition> THEN

<statement(s)>

ELSIF

<statement(s)>

END IF;


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Loop exampleDECLARE

i NUMBER := 1;BEGIN

LOOP INSERT INTO T1

VALUES(i,i); i := i+1; EXIT WHEN i>100;

END LOOP; END; /

DECLARE i NUMBER := 1;

BEGIN LOOP

INSERT INTO T1VALUES(i,i);

i := i+1; EXIT WHEN i>100;

END LOOP; END; /


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Cursors in PL/SQL As expected, PL/SQL has syntax to do the usual

things: Declare cursors Open and close Fetch and eventually leave

Each can be done manually Also has elegant for/cursor loop

Declare, open, close, fetch all automatic:

Example: http://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/for.sql

FOR my-rec IN my-cursor LOOP…END LOOP;

FOR my-rec IN my-cursor LOOP…END LOOP;


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Functions Like procedures but with return values

Big strength: can be called from SQL

CREATE FUNCTION <functionName> (<paramList>) RETURNS type AS

<localDeclarations>BEGIN<functionBody>END;

CREATE FUNCTION <functionName> (<paramList>) RETURNS type AS

<localDeclarations>BEGIN<functionBody>END;

DROP FUNCTION <functionName>;DROP FUNCTION <functionName>;


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Function example Like procedures but with return values

drop in same way Big strength: can be called from SQL

http://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/maxval.sql

CREATE OR REPLACE FUNCTION maxval(a IN int, b IN int) RETURN int ASBEGIN IF a > b THEN RETURN a; ELSE RETURN b; END IF;END maxval; /

CREATE OR REPLACE FUNCTION maxval(a IN int, b IN int) RETURN int ASBEGIN IF a > b THEN RETURN a; ELSE RETURN b; END IF;END maxval; /

INSERT INTO R VALUES(“abc”, maxval(5,10));INSERT INTO R VALUES(“abc”, maxval(5,10));


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How to run scripts Don’t want to type ftns into sqlplus by hand Define them in a .sql file In sqlplus, execute .sql file

Runs commands in file Here, defines function

Now, we can call functions

Seehttp://pages.stern.nyu.edu/~mjohnson/dbms/eg/lec19/plsql.txt

SQL> @maxval.sqlSQL> @maxval.sql

SQL> exec DBMS_OUTPUT.PUT_LINE (maxval(5,10))SQL> exec DBMS_OUTPUT.PUT_LINE (maxval(5,10))


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Triggers in Oracle Oracle triggers are written in PL/SQL Trigger body is like regular procedure body,

but following trigger syntax:

CREATE OR REPLACE TRIGGER MYTRIG1 BEFORE DELETE ON mytable BEGIN--codeEND;

CREATE OR REPLACE TRIGGER MYTRIG1 BEFORE DELETE ON mytable BEGIN--codeEND;


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Look up procedures, functions In Oracle, functions & procedures in

user_procedures:

SELECT object_name from user_procedures;SELECT object_name from user_procedures;


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More on PL/SQL O’Reilly’s Oracle PL/SQL Programming:

http://www.unix.org.ua/orelly/oracle/prog2/

PL/SQL Reference & Tutorial: http://www.ilook.fsnet.co.uk/ora_sql/sqlmain2.htm

Introduction to PL/SQL: http://www.geocities.com/cliktoprogram/plsql/introduction.ht

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Oracle FAQ's Script and Code Exchange: http://www.orafaq.com/scripts/

C20.0046: Database Management Systems Lecture #19

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