Matthew P. Johnson, OCL3, CISDD CUNY, June OCL3 Oracle 10g: SQL & PL/SQL Session #7 Matthew P. Johnson CISDD, CUNY June, 2005

Matthew P. Johnson, OCL3, CISDD CUNY, June Agenda Last time:  Programming for SQL  Pro*C, JDBC This time:  SPs in PL/SQL Next time:  More PL/SQL  Triggers

Matthew P. Johnson, OCL3, CISDD CUNY, June Step back Recall basic problem: need SQL plus stronger programming lang   need to connect the two langs In all these cases (and in the web app case), idea is: put SQL in (traditional-lang) programs Another way: put programs in SQL  i.e., store programs on the DBMS  “stored procedures”

Matthew P. Johnson, OCL3, CISDD CUNY, June Next topic: SPs “Persistent, Stored Modules” / “Stored Procedures / “PL/SQL programs” (in Oracle) 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!

Matthew P. Johnson, OCL3, CISDD CUNY, June Integration with SQL DECLARE l_book_count INTEGER; BEGIN SELECT COUNT(*) INTO l_book_count FROM books WHERE author LIKE '%FEUERSTEIN, STEVEN%'; DBMS_OUTPUT.PUT_LINE ( 'Steven has written (or co-written) ' || l_book_count || ' books.'); -- Oh, and I changed my name, so... UPDATE books SET author = REPLACE (author, 'STEVEN', 'STEPHEN') WHERE author LIKE '%FEUERSTEIN, STEVEN%'; END; DECLARE l_book_count INTEGER; BEGIN SELECT COUNT(*) INTO l_book_count FROM books WHERE author LIKE '%FEUERSTEIN, STEVEN%'; DBMS_OUTPUT.PUT_LINE ( 'Steven has written (or co-written) ' || l_book_count || ' books.'); -- Oh, and I changed my name, so... UPDATE books SET author = REPLACE (author, 'STEVEN', 'STEPHEN') WHERE author LIKE '%FEUERSTEIN, STEVEN%'; END;

Matthew P. Johnson, OCL3, CISDD CUNY, June 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 procedure  how return works

Matthew P. Johnson, OCL3, CISDD CUNY, June PL/SQL Generally speaking can be used wherever SQL can be  sqlplus  embeded SQL  JDBC Can store programs in files (.sql), run later runs code in myprog.sql

Matthew P. Johnson, OCL3, CISDD CUNY, June 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 Though now compiled to bytecode or (optionally) to native  Don’t require functions/procedures Though now supported  Weakly typed Lots of auto-conversion

Matthew P. Johnson, OCL3, CISDD CUNY, June PL/SQL: Hello, World BEGIN -- print out message DBMS_OUTPUT.PUT_LINE('Hello World, from PL/SQL'); END; / BEGIN -- print out message DBMS_OUTPUT.PUT_LINE('Hello World, from PL/SQL'); END; /

Matthew P. Johnson, OCL3, CISDD CUNY, June Hello, World Try again… 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; /

Matthew P. Johnson, OCL3, CISDD CUNY, June Use start-up script Go to \sqlplus\admin\glogin.sql Start-up script run upon login to SQL*Plus Add “SET SERVEROUTPUT ON” to it If running non-i version of SQL*Plus, also looks in current dir for login.sql script

Matthew P. Johnson, OCL3, CISDD CUNY, June How to run code The code before ended with a forward slash Not SQL and not PL/SQL – just for SQL*Plus to tell it to run the code entered Must go on its own line  O.w., will be ignored and then interpreted as part of code, causing an error To call a procedure in SQL*Plus, can also use execute/exec: exec DBMS_OUTPUT.PUT_LINE('Hello World, from PL/SQL')

Matthew P. Johnson, OCL3, CISDD CUNY, June How to run code EXEC is just short-hand: SQL> exec dbms_output.put_line('hi '); dbms_output.put_line('there'

Matthew P. Johnson, OCL3, CISDD CUNY, June PL/SQL operators/symbols ;end statement %attribute indicator (cursor attributes like %ISOPEN and indirect declaration attributes like %ROWTYPE :host variable indicator <> and !=not-equal-to =equal-to :=assignment op ** exponentiation operator --, /* and */, rem comments

Matthew P. Johnson, OCL3, CISDD CUNY, June Var names identifiers limited to 30 alpha-num chars  Must start with letter, $, _, or # E.g.: abc, $a$, $$$ PL/SQL is case Insensitive  abc, ABC, AbC all the same  Unless you use double-quotes… Also supports constants:  Varname datatype CONSTANT := val;

Matthew P. Johnson, OCL3, CISDD CUNY, June Literals Numbers: 123, 12.3, 3.05E19, 12e-5, null String: ‘abc’, ‘AbC’, null  String comparison is case-SENSitive Boolean: true, false, null  true != ‘true’ No date literals, as in regular SQL  To_date('31-JAN-94') Escape single-quotes in strings with two single- quotes ‘it’’s’  it’s ''''''  ''

Matthew P. Johnson, OCL3, CISDD CUNY, June Blocks PL/SQL is a block-structured language Block = seq. of instructions, with scope Can have anonymous blocks And named blocks  Procedures  Functions

Matthew P. Johnson, OCL3, CISDD CUNY, June Structure of a block As in Pascal, var declars precede body header--if named DECLARE--optional --var declarations BEGIN --executable statements --queries/updates, etc. EXCEPTION--optional --catch exceptions END; /--to execute header--if named DECLARE--optional --var declarations BEGIN --executable statements --queries/updates, etc. EXCEPTION--optional --catch exceptions END; /--to execute

Matthew P. Johnson, OCL3, CISDD CUNY, June 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; /

Matthew P. Johnson, OCL3, CISDD CUNY, June 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 ( ) AS ; CREATE PROCEDURE ( ) AS ; DROP PROCEDURE ; CREATE OR REPLACE PROCEDURE ( ) AS ; CREATE OR REPLACE PROCEDURE ( ) AS ;

Matthew P. Johnson, OCL3, CISDD CUNY, June Example procedure Define the procedure: Now we can call it: CREATE PROCEDURE testProcedure AS BEGIN INSERT INTO Student VALUES (5, 'Joe'); COMMIT; END; CREATE PROCEDURE testProcedure AS BEGIN INSERT INTO Student VALUES (5, 'Joe'); COMMIT; END; EXEC testProcedure

Matthew P. Johnson, OCL3, CISDD CUNY, June 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

Matthew P. Johnson, OCL3, CISDD CUNY, June Procedure I/O example A procedure to take a beer and price and add it to Joe's menu: Sells(bar, beer, price) CREATE PROCEDURE izzyMenu( b IN char(20), p IN double) AS BEGIN INSERT INTO Sells VALUES(‘Izzy’’s', b, p); END; / CREATE PROCEDURE izzyMenu( b IN char(20), p IN double) AS BEGIN INSERT INTO Sells VALUES(‘Izzy’’s', b, p); END; / Are these the right types?

Matthew P. Johnson, OCL3, CISDD CUNY, June Procedure I/O example A procedure to take a beer and price and add it to Joe's menu: Sells(bar, beer, price) CREATE PROCEDURE izzyMenu( b IN Sells.beer%TYPE, p IN Sells.price%TYPE) AS BEGIN INSERT INTO Sells VALUES(‘Izzy’’s', b, p); END; / CREATE PROCEDURE izzyMenu( b IN Sells.beer%TYPE, p IN Sells.price%TYPE) AS BEGIN INSERT INTO Sells VALUES(‘Izzy’’s', b, p); END; /

Matthew P. Johnson, OCL3, CISDD CUNY, June Larger procedure e.g. CREATE or replace PROCEDURE hike_prices(old_price number, new_price out number, percent_hike number := 5) is Begin new_price := old_price + old_price * percent_hike/100; End; / CREATE or replace PROCEDURE hike_prices(old_price number, new_price out number, percent_hike number := 5) is Begin new_price := old_price + old_price * percent_hike/100; End; /

Matthew P. Johnson, OCL3, CISDD CUNY, June Call the procedure But how to use to modify table data? Convert to a function Declare currprice number := 20; newprice number; Begin hike_prices(currprice,newprice,5); dbms_output.put_line(newprice); End; Declare currprice number := 20; newprice number; Begin hike_prices(currprice,newprice,5); dbms_output.put_line(newprice); End;

Matthew P. Johnson, OCL3, CISDD CUNY, June Functions Like procedures but with return values Big strength: can be called from SQL CREATE FUNCTION ( ) RETURN type AS BEGIN END; CREATE FUNCTION ( ) RETURN type AS BEGIN END; DROP FUNCTION ;

Matthew P. Johnson, OCL3, CISDD CUNY, June Function example 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));

Matthew P. Johnson, OCL3, CISDD CUNY, June Hike function Now can use directly in update statements NB: had to use different name for ftn  Same namespace for ftns & procs, although different CREATE or replace FUNCTION hike_pricesf(old_price number, percent_hike number := 5) return number is Begin return old_price + old_price * percent_hike/100; End; / CREATE or replace FUNCTION hike_pricesf(old_price number, percent_hike number := 5) return number is Begin return old_price + old_price * percent_hike/100; End; /

Matthew P. Johnson, OCL3, CISDD CUNY, June 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))

Matthew P. Johnson, OCL3, CISDD CUNY, June How to run scripts Can also use the start command: If no file extension is given,.sql is assumed Can use full paths: Scripts can call other scripts for current dir, for dir of current script Scripts are not (by default) echoed. Can use: SQL> START maxval.sql SQL> SET ECHO ON

Matthew P. Johnson, OCL3, CISDD CUNY, June Stored ftns & procs persist Once a function or procedure is created, it persists until it’s dropped Stored procs are stored in the DB itself  In user_procedures in Oracle Also, can describe ftns and procs: CREATE OR REPLACE FUNCTION … SELECT object_name from user_procedures; SQL> describe wordcount

Matthew P. Johnson, OCL3, CISDD CUNY, June Word count program CREATE OR REPLACE FUNCTION wordcount (str IN VARCHAR2) RETURN PLS_INTEGER AS /* words PLS_INTEGER := 0; ***Commented out for intentional error*** */ len PLS_INTEGER := NVL(LENGTH(str),0); inside_a_word BOOLEAN; BEGIN FOR i IN 1..len + 1 LOOP IF ASCII(SUBSTR(str, i, 1)) len THEN IF inside_a_word THEN words := words + 1; inside_a_word := FALSE; END IF; ELSE inside_a_word := TRUE; END IF; END LOOP; RETURN words; END; CREATE OR REPLACE FUNCTION wordcount (str IN VARCHAR2) RETURN PLS_INTEGER AS /* words PLS_INTEGER := 0; ***Commented out for intentional error*** */ len PLS_INTEGER := NVL(LENGTH(str),0); inside_a_word BOOLEAN; BEGIN FOR i IN 1..len + 1 LOOP IF ASCII(SUBSTR(str, i, 1)) len THEN IF inside_a_word THEN words := words + 1; inside_a_word := FALSE; END IF; ELSE inside_a_word := TRUE; END IF; END LOOP; RETURN words; END;

Matthew P. Johnson, OCL3, CISDD CUNY, June Intermission Fill out evals Scottish Parliament/Outer join exercises Work on exercises 1-3 of lab 7

Matthew P. Johnson, OCL3, CISDD CUNY, June Getting errors Simply says: To get actual errors, say SHOW ERR(ORS) Can also get errors per object: Warning: must get object type right! Can also look at user_errors tbl directly Warning: Function created with compilation errors. SQL> show errors function wordcount

Matthew P. Johnson, OCL3, CISDD CUNY, June Calling functions and procedures Procedures can simple executed, ftns can’t How to just call a ftn? Can use dbms_output, as seen Can also select the ftn value from dual SQL> select(wordcount(‘hi there’) from dual;

Matthew P. Johnson, OCL3, CISDD CUNY, June Agenda A little more PL/SQL lecture Go through some SQL lab exercises? Evals More PL/SQL lecture/lab… Later: go through some PL/SQL exercises…

Matthew P. Johnson, OCL3, CISDD CUNY, June Look up procedures, functions In Oracle, functions & procedures in user_procedures: Also, can describe ftns and procs: SELECT object_name from user_procedures; SQL> describe wordcount

Matthew P. Johnson, OCL3, CISDD CUNY, June Subblocks Blocks may contain blocks, for narrower scope: CREATE OR REPLACE PROCEDURE calc_totals IS year_total NUMBER; BEGIN year_total := 0; /* Nested anonymous block */ DECLARE month_total NUMBER; BEGIN month_total := year_total / 12; END; CREATE OR REPLACE PROCEDURE calc_totals IS year_total NUMBER; BEGIN year_total := 0; /* Nested anonymous block */ DECLARE month_total NUMBER; BEGIN month_total := year_total / 12; END;

Matthew P. Johnson, OCL3, CISDD CUNY, June More on scope Can name blocks and loops with labels > BEGIN INSERT INTO catalog VALUES (...); EXCEPTION WHEN DUP_VAL_ON_INDEX THEN NULL; END insert_but_ignore_dups; > BEGIN INSERT INTO catalog VALUES (...); EXCEPTION WHEN DUP_VAL_ON_INDEX THEN NULL; END insert_but_ignore_dups;

Matthew P. Johnson, OCL3, CISDD CUNY, June Scope and nested, labeled loops > DECLARE counter INTEGER := 0; BEGIN... DECLARE counter INTEGER := 1; BEGIN IF counter = outerblock.counter THEN... END IF; END; > DECLARE counter INTEGER := 0; BEGIN... DECLARE counter INTEGER := 1; BEGIN IF counter = outerblock.counter THEN... END IF; END;

Matthew P. Johnson, OCL3, CISDD CUNY, June Scope and nested, labeled loops BEGIN > LOOP EXIT outer_loop; END LOOP; some_statement ; END LOOP; END; BEGIN > LOOP EXIT outer_loop; END LOOP; some_statement ; END LOOP; END;

Matthew P. Johnson, OCL3, CISDD CUNY, June 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;

Matthew P. Johnson, OCL3, CISDD CUNY, June More ifs IF ELSE END IF; IF ELSE END IF; IF ELSEIF ELSE END IF; IF ELSEIF ELSE END IF;

Matthew P. Johnson, OCL3, CISDD CUNY, June Multiple elsifs An if statement can have multiple elseifs: IF salary >= AND salary <= THEN give_bonus(employee_id, 1500); ELSIF salary > AND salary <= THEN give_bonus(employee_id, 1000); ELSIF salary > THEN give_bonus(employee_id, 400); END IF; IF salary >= AND salary <= THEN give_bonus(employee_id, 1500); ELSIF salary > AND salary <= THEN give_bonus(employee_id, 1000); ELSIF salary > THEN give_bonus(employee_id, 400); END IF;

Matthew P. Johnson, OCL3, CISDD CUNY, June Nested ifs As usual, if statements can be nested: Can often be replaced with an ANDed condition IF condition1 THEN IF condition2 THEN statements2 ELSE IF condition3 THEN statements3 ELSIF condition4 THEN statements4 END IF; IF condition1 THEN IF condition2 THEN statements2 ELSE IF condition3 THEN statements3 ELSIF condition4 THEN statements4 END IF;

Matthew P. Johnson, OCL3, CISDD CUNY, June 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; /

Matthew P. Johnson, OCL3, CISDD CUNY, June More loops Infinite loop: while loop: LOOP executable_statements; END LOOP; LOOP executable_statements; END LOOP; WHILE condition LOOP executable_statements; END LOOP; WHILE condition LOOP executable_statements; END LOOP;

Matthew P. Johnson, OCL3, CISDD CUNY, June More loops Numerical for loop: Cursor for loop: FOR for_index IN low_value.. high_value LOOP executable_statements; END LOOP; FOR for_index IN low_value.. high_value LOOP executable_statements; END LOOP; FOR record_index IN my_cursor LOOP executable_statements; END LOOP; FOR record_index IN my_cursor LOOP executable_statements; END LOOP;

Matthew P. Johnson, OCL3, CISDD CUNY, June Programs and rights By default, only the creator of a program may run it (apart from the admin) If others should run, must GRANT them permission: Permissions can be revoked: Can also grant to particular roles or everyone: Wider/narrower grant ops are independent… SQL> GRANT EXECUTE ON wordcount TO george; SQL> REVOKE EXECUTE FROM wordcount TO george; SQL> GRANT EXECUTE ON wordcount TO dba_role; SQL> GRANT EXECUTE ON wordcount TO public; SQL> GRANT EXECUTE ON wordcount TO dba_role; SQL> GRANT EXECUTE ON wordcount TO public;