M.P. Johnson, DBMS, Stern/NYU, Sp20041 C : Database Management Systems Lecture #19 Matthew P. Johnson Stern School of Business, NYU Spring, 2004

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

M.P. Johnson, DBMS, Stern/NYU, Sp Recap: JDBC Host language + Embedded SQL Preprocessor Host Language + function calls Host language compiler Executable Preprocessor Host language compiler Oracle’s Pro*C javac + jar prog.pc Prog.java Proj.class

M.P. Johnson, DBMS, Stern/NYU, Sp 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();...

M.P. Johnson, DBMS, Stern/NYU, Sp Also: ODBC Used by Microsoft platforms/tools, others Access:  Start | Control Panel | Administrative Tools | Data Sources (ODBC) Similar to JDBC Won’t cover

M.P. Johnson, DBMS, Stern/NYU, Sp 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}

M.P. Johnson, DBMS, Stern/NYU, Sp 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”

M.P. Johnson, DBMS, Stern/NYU, Sp 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!

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

M.P. Johnson, DBMS, Stern/NYU, Sp PL/SQL Generally speaking can be used wherever SQL can be  sqlplus  embeded SQL Can store programs in files (.sql), run later runs code in myprog.sql

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

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

M.P. Johnson, DBMS, Stern/NYU, Sp PL/SQL: Hello, World 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; /

M.P. Johnson, DBMS, Stern/NYU, Sp PL/SQL code examples One example:  Likes(drinker, beverage) Another example:  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; /

M.P. Johnson, DBMS, Stern/NYU, Sp 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 ( ) ; CREATE PROCEDURE ( ) ; DROP PROCEDURE ; CREATE OR REPLACE PROCEDURE ( ) ; CREATE OR REPLACE PROCEDURE ( ) ;

M.P. Johnson, DBMS, Stern/NYU, Sp Example procedure Define the procedure: Now we can call it: CREATE PROCEDURE testProcedure BEGIN INSERT INTO Student VALUES (5, ‘Joe’); COMMIT; END; CREATE PROCEDURE testProcedure BEGIN INSERT INTO Student VALUES (5, ‘Joe’); COMMIT; END; EXEC testProcedure;

M.P. Johnson, DBMS, Stern/NYU, Sp 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%TYPE

M.P. Johnson, DBMS, Stern/NYU, Sp 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 BEGIN INSERT INTO Sells VALUES('Joe''s Bar', b, p); END; / CREATE PROCEDURE joeMenu( b IN Sells.beer%TYPE, p IN Sells.price%TYPE) AS BEGIN INSERT INTO Sells VALUES('Joe''s Bar', b, p); END; /

M.P. Johnson, DBMS, Stern/NYU, Sp Branching IF–THEN statements use THEN Must end with END IF Use ELSIF in place of ELSE IF Example:  IF THEN ELSIF END IF; IF THEN ELSIF END IF;

M.P. Johnson, DBMS, Stern/NYU, Sp Loop example DECLARE 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 T1 VALUES(i,i); i := i+1; EXIT WHEN i>100; END LOOP; END; /

M.P. Johnson, DBMS, Stern/NYU, Sp 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:  FOR my-rec IN my-cursor LOOP … END LOOP; FOR my-rec IN my-cursor LOOP … END LOOP;

M.P. Johnson, DBMS, Stern/NYU, Sp Functions Like procedures but with return values Big strength: can be called from SQL CREATE FUNCTION ( ) RETURNS type AS BEGIN END; CREATE FUNCTION ( ) RETURNS type AS BEGIN END; DROP FUNCTION ;

M.P. Johnson, DBMS, Stern/NYU, Sp Function example Like procedures but with return values  drop in same way  Big strength: can be called from SQL CREATE OR REPLACE FUNCTION maxval(a IN int, b IN int) RETURN int AS BEGIN 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 AS BEGIN IF a > b THEN RETURN a; ELSE RETURN b; END IF; END maxval; / INSERT INTO R VALUES(“abc”, maxval(5,10));

M.P. Johnson, DBMS, Stern/NYU, Sp 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 See SQL> exec DBMS_OUTPUT.PUT_LINE (maxval(5,10))

M.P. Johnson, DBMS, Stern/NYU, Sp 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 --code END; CREATE OR REPLACE TRIGGER MYTRIG1 BEFORE DELETE ON mytable BEGIN --code END;

M.P. Johnson, DBMS, Stern/NYU, Sp Look up procedures, functions In Oracle, functions & procedures in user_procedures: SELECT object_name from user_procedures;

M.P. Johnson, DBMS, Stern/NYU, Sp More on PL/SQL O’Reilly’s Oracle PL/SQL Programming:  PL/SQL Reference & Tutorial:  Introduction to PL/SQL:  ml ml Oracle FAQ's Script and Code Exchange: 