stored.ppt

Stored Procedure Language
Stored Procedure Overview
•Stored Procedure is a function in a shared library accessible
to the database server
•can also write stored procedures using languages such as C
or Java
•Advantages of stored procedure : Reduced network traffic
•The more SQL statements that are grouped together for
execution, the larger the savings in network traffic

Applications using
stored procedures

Writing Stored Procedures
• Allows local variables, loops, procedures, examinationof one tuple ar a time.
Rough Form
DECLARE
Declarations
BEGIN
Executable statements
END
@
 The DECLARE portion is optional
 Alternate terminating character in DB2 CLP scripts: ('@'), needed for ending and
running.

Simplest Form : Sequence of Modifications
Employee( name , ssn, salary)
BEGIN
INSERT INTO EMPLOYEE VALUES (‘Sharad’, 123, 234);
DELETE FROM EMPLOYEE WHERE ssn = 234;
END
@
To process the DB2 CLP script from the command line:
db2 -tdterm-char -vf script-name
Writing Stored Procedures
 Tasks performed by the client application
 Tasks performed by the stored procedure, when invoked
 The CALL statement
 Explicit parameter to be defined :
 IN: Passes a value to the stored procedure from the client application
 OUT: Stores a value that is passed to the client application when the stored procedure terminates.
 INOUT : Passes a value to the stored procedure from the client application, and returns a value to the
Client application when the stored procedure terminates

CREATE OR REPLACE PROCEDURE <name> (<arglist>) AS <declarations>
BEGIN
<procedure statements>
END
@
EXAMPLE:
CREATE PROCEDURE UPDATE_SALARY_1 (1)
(IN EMPLOYEE_NUMBER CHAR(6), (2)
IN RATE INTEGER) (2)
LANGUAGE SQL (3)
BEGIN
UPDATE EMPLOYEE (4)
SET SALARY = SALARY * (1.0 * RATE / 100.0 )
WHERE SSN = EMPLOYEE_NUMBER;
END
LANGUAGE value of SQL and the BEGIN...END block, which forms the procedure body, are particular to an
SQL procedure
1)The stored procedure name is UPDATE_SALARY_1.
2)The two parameters have data types of CHAR(6) and INTEGER. Both are input parameters.
3)LANGUAGE SQL indicates that this is an SQL procedure, so a procedure body follows the other
parameters.
4)The procedure body consists of a single SQL UPDATE statement, which updates rows in the
employee table.

Some Valid SQL Procedure Body Statements
 CASE statement
 FOR statement
 GOTO statement
 IF statement
 ITERATE statement
 RETURN statement
 WHILE statement

• Invoking Procedures
Can invoke Stored procedure stored at the location of the database by using the
SQL CALL statement
• Nested SQL Procedures:
To call a target SQL procedure from within a caller SQL procedure, simply include
a CALL statement with the appropriate number and types of parameters in your
caller.
CREATE PROCEDURE NEST_SALES(OUT budget DECIMAL(11,2))
LANGUAGE SQL
BEGIN
DECLARE total INTEGER DEFAULT 0;
SET total = 6;
CALL SALES_TARGET(total);
SET budget = total * 10000;
END

CONDITIONAL STATEMENTS:
IF <condition> THEN
<statement(s)>
ELSE
<statement(s)>
END IF;
Loops
LOOP
……
EXIT WHEN <condition>
……
END LOOP;

EXAMPLE :
CREATE PROCEDURE UPDATE_SALARY_IF
(IN employee_number CHAR(6), IN rating SMALLINT)
LANGUAGE SQL
BEGIN
SET counter = 10;
WHILE (counter > 0) DO
IF (rating = 1)
THEN UPDATE employee
SET salary = salary * 1.10, bonus = 1000
WHERE empno = employee_number;
ELSEIF (rating = 2)
THEN UPDATE employee
ELSE UPDATE employee
END IF;
SET counter = counter – 1;
END WHILE;
END
@

EXAMPLE :
The procedure receives a department number as an input parameter. A WHILE statement in the
procedure body fetches the salary and bonus for each employee in the department. An IF
statement within the WHILE statement updates salaries for each employee depending on
number of years of service and current salary. When all employee records in the department
have been processed, the FETCH statement that retrieves employee records receives
SQLSTATE 20000. A not_found condition handler makes the search condition for the WHILE
statement false, so execution of the WHILE statement ends.
CREATE PROCEDURE BUMP_SALARY_IF (IN deptnumber SMALLINT)
LANGUAGE SQL
BEGIN
DECLARE v_salary DOUBLE;
DECLARE v_years SMALLINT;
DECLARE v_id SMALLINT;
DECLARE at_end INT DEFAULT 0;
DECLARE not_found CONDITION FOR SQLSTATE '02000';
-- CAST salary as DOUBLE because SQL procedures do not support DECIMAL
DECLARE C1 CURSOR FOR
SELECT id, CAST(salary AS DOUBLE), years
FROM staff;
DECLARE CONTINUE HANDLER FOR not_found
SET at_end = 1;

OPEN C1;
FETCH C1 INTO v_id, v_salary, v_years;
WHILE at_end = 0 DO
IF (v_salary < 2000 * v_years)
THEN UPDATE staff
SET salary = 2150 * v_years
WHERE id = v_id;
ELSEIF (v_salary < 5000 * v_years)
THEN IF (v_salary < 3000 * v_years)
THEN UPDATE staff
SET salary = 3000 * v_years
WHERE id = v_id;
ELSE UPDATE staff
SET salary = v_salary * 1.10
WHERE id = v_id;
END IF;
ELSE UPDATE staff
SET job = 'PREZ'
WHERE id = v_id;
END IF;
FETCH C1 INTO v_id, v_salary, v_years;
END WHILE;
CLOSE C1;
END

stored.ppt

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