OCL3 Oracle 10 g : SQL & PL/SQL Session #7

Matthew P. Johnson, OCL3, CISDD CUNY, June 2005

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OCL3 Oracle 10g:SQL & PL/SQLSession #7

Matthew P. Johnson

CISDD, CUNY

June, 2005


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Agenda Last time:

Programming for SQL Pro*C, JDBC

This time: SPs in PL/SQL

Next time: More PL/SQL Triggers


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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”


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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!


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Integration with SQLDECLARE

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')


END;

DECLARE

l_book_count INTEGER;

BEGIN

SELECT COUNT(*)

INTO l_book_count

FROM books


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')


END;


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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 procedure how return works


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PL/SQL Generally speaking can be used wherever

SQL can be sqlplus embeded SQL JDBC

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 Though now compiled to bytecode or (optionally) to native

Don’t require functions/procedures Though now supported

Weakly typed Lots of auto-conversion


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

BEGIN

-- print out message

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

END;

/

BEGIN



END;

/


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Hello, World Try again…

SET SERVEROUTPUT ON

BEGIN



END;

/

SET SERVEROUTPUT ON

BEGIN



END;

/


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Use start-up script Go to <Orahome>\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


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


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How to run code EXEC is just short-hand:

SQL> exec dbms_output.put_line('hi '); dbms_output.put_line('there'

SQL> exec dbms_output.put_line('hi '); dbms_output.put_line('there'


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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


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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;


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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 '''''' ''


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Blocks PL/SQL is a block-structured language

Block = seq. of instructions, with scope Can have anonymous blocks And named blocks

Procedures Functions


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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


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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>) AS

<procedure body as above>;

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

<procedure body as above>;

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

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

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


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Example procedure Define the procedure:

Now we can call it:

CREATE PROCEDURE testProcedure ASBEGIN

INSERT INTO Student VALUES (5, 'Joe');COMMIT;

END;

CREATE PROCEDURE testProcedure ASBEGIN

INSERT INTO Student VALUES (5, 'Joe');COMMIT;

END;

EXEC testProcedureEXEC 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 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

BEGININSERT INTO SellsVALUES(‘Izzy’’s', b, p);

END;/

CREATE PROCEDURE izzyMenu(b IN char(20),p IN double) AS


END;/

Are these the right types?


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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


END;/

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


END;/


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Larger procedure e.g.

CREATE or replace PROCEDURE hike_prices(old_price number, new_price out number, percent_hike number := 5) is

Beginnew_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

Beginnew_price := old_price + old_price * percent_hike/100;

End;/


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Call the procedure

But how to use to modify table data?

Convert to a function

Declarecurrprice number := 20;newprice number;

Beginhike_prices(currprice,newprice,5);dbms_output.put_line(newprice);

End;

Declarecurrprice number := 20;newprice number;

Beginhike_prices(currprice,newprice,5);dbms_output.put_line(newprice);

End;


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Functions Like procedures but with return values

Big strength: can be called from SQL

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

<localDeclarations>BEGIN<functionBody>END;

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

<localDeclarations>BEGIN<functionBody>END;

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


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Function example

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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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

Beginreturn old_price + old_price * percent_hike/100;

End;/

CREATE or replace FUNCTION hike_pricesf(old_price number, percent_hike number := 5) return number is

Beginreturn old_price + old_price * percent_hike/100;

End;/


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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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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 Use @ for current dir, @@ for dir of current script Scripts are not (by default) echoed. Can use:

SQL> START maxval.sqlSQL> START maxval.sql

SQL> @c:\somewhere\maxval.sqlSQL> @c:\somewhere\maxval.sql

SQL> SET ECHO ONSQL> SET ECHO ON


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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 …CREATE OR REPLACE FUNCTION …

SELECT object_name from user_procedures;SELECT object_name from user_procedures;

SQL> describe wordcountSQL> describe wordcount


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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)) < 33 OR i > 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)) < 33 OR i > 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;

http://pages.stern.nyu.edu/~mjohnson/dbms/plsql/wordcount.sql


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Intermission Fill out evals

Scottish Parliament/Outer join exercises

Work on exercises 1-3 of lab 7


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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.Warning: Function created with compilation errors.

SQL> show errors function wordcountSQL> show errors function wordcount


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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;SQL> select(wordcount(‘hi there’) from dual;


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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…


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

user_procedures:

Also, can describe ftns and procs:

SELECT object_name from user_procedures;SELECT object_name from user_procedures;

SQL> describe wordcountSQL> describe wordcount


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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;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;END;


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More on scope Can name blocks and loops with labels

<<insert_but_ignore_dups>>BEGIN INSERT INTO catalog VALUES (...);EXCEPTION WHEN DUP_VAL_ON_INDEX THEN NULL;END insert_but_ignore_dups;

<<insert_but_ignore_dups>>BEGIN INSERT INTO catalog VALUES (...);EXCEPTION WHEN DUP_VAL_ON_INDEX THEN NULL;END insert_but_ignore_dups;


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Scope and nested, labeled loops<<outerblock>>DECLARE counter INTEGER := 0;BEGIN ... DECLARE counter INTEGER := 1; BEGIN IF counter = outerblock.counter THEN ... END IF; END;END;

<<outerblock>>DECLARE counter INTEGER := 0;BEGIN ... DECLARE counter INTEGER := 1; BEGIN IF counter = outerblock.counter THEN ... END IF; END;END;


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Scope and nested, labeled loops

BEGIN <<outer_loop>> LOOP LOOP EXIT outer_loop; END LOOP; some_statement ; END LOOP;END;

BEGIN <<outer_loop>> LOOP LOOP EXIT outer_loop; END LOOP; some_statement ; END LOOP;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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More ifs

IF <condition>

ELSE

END IF;

IF <condition>

ELSE

END IF;

IF <expression>

ELSEIF <expression>

ELSE

END IF;

IF <expression>

ELSEIF <expression>

ELSE

END IF;


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Multiple elsifs An if statement can have multiple elseifs:

IF salary >= 10000 AND salary <= 20000

THEN give_bonus(employee_id, 1500);

ELSIF salary > 20000 AND salary <= 40000


ELSIF salary > 40000


END IF;

IF salary >= 10000 AND salary <= 20000


ELSIF salary > 20000 AND salary <= 40000


ELSIF salary > 40000


END IF;


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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;

END IF;

END IF;

IF condition1

THEN

IF condition2

THEN

statements2

ELSE

IF condition3

THEN

statements3

ELSIF condition4

THEN

statements4

END IF;

END IF;

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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More loops Infinite loop:

while loop:

LOOP

executable_statements;

END LOOP;

LOOP


END LOOP;

WHILE condition

LOOP


END LOOP;

WHILE condition

LOOP


END LOOP;


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More loops Numerical for loop:

Cursor for loop:

FOR for_index IN low_value .. high_value

LOOP


END LOOP;

FOR for_index IN low_value .. high_value

LOOP


END LOOP;

FOR record_index IN my_cursor

LOOP


END LOOP;

FOR record_index IN my_cursor

LOOP


END LOOP;


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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> GRANT EXECUTE ON wordcount TO george;

SQL> REVOKE EXECUTE FROM 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;

Documents

OCL3 Oracle 10 g : SQL & PL/SQL Session #7