DB2 Version 10.1 for Linux, UNIX, and Windows

Simple CASE statement (PL/SQL)

The simple CASE statement attempts to match an expression (known as the selector) to another expression that is specified in one or more WHEN clauses. A match results in the execution of one or more corresponding statements.

Syntax


>>-CASE--selector-expression------------------------------------>

   .----------------------------------------------.   
   |                               .------------. |   
   V                               V            | |   
>----WHEN--match-expression--THEN----statements-+-+------------->

>--+----------------------+--END CASE--------------------------><
   |       .------------. |             
   |       V            | |             
   '-ELSE----statements-+-'

Description

CASE selector-expression: Specifies an expression whose value has a data type that is compatible with each match-expression. If the value of selector-expression matches the first match-expression, the statements in the corresponding THEN clause are executed. If there are no matches, the statements in the corresponding ELSE clause are executed. If there are no matches and there is no ELSE clause, an exception is thrown.
WHEN match-expression: Specifies an expression that is evaluated within the CASE statement. If selector-expression matches a match-expression, the statements in the corresponding THEN clause are executed.
THEN: A keyword that introduces the statements that are to be executed when the corresponding Boolean expression evaluates to TRUE.
statements: Specifies one or more SQL or PL/SQL statements, each terminated with a semicolon.
ELSE: A keyword that introduces the default case of the CASE statement.

Example

The following example uses a simple CASE statement to assign a department name and location to a variable that is based upon the department number.

DECLARE
    v_empno         emp.empno%TYPE;
    v_ename         emp.ename%TYPE;
    v_deptno        emp.deptno%TYPE;
    v_dname         dept.dname%TYPE;
    v_loc           dept.loc%TYPE;
    CURSOR emp_cursor IS SELECT empno, ename, deptno FROM emp;
BEGIN
    OPEN emp_cursor;
    DBMS_OUTPUT.PUT_LINE('EMPNO    ENAME     DEPTNO    DNAME     '
        || '     LOC');
    DBMS_OUTPUT.PUT_LINE('-----    -------   ------    ----------'
        || '     ---------');
    LOOP
        FETCH emp_cursor INTO v_empno, v_ename, v_deptno;
        EXIT WHEN emp_cursor%NOTFOUND;
        CASE v_deptno
            WHEN 10 THEN v_dname := 'Accounting';
                         v_loc   := 'New York';
            WHEN 20 THEN v_dname := 'Research';
                         v_loc   := 'Dallas';
            WHEN 30 THEN v_dname := 'Sales';
                         v_loc   := 'Chicago';
            WHEN 40 THEN v_dname := 'Operations';
                         v_loc   := 'Boston';
            ELSE v_dname := 'unknown';
                         v_loc   := '';
        END CASE;
        DBMS_OUTPUT.PUT_LINE(v_empno || '     ' || RPAD(v_ename, 10) ||
            '  ' || v_deptno || '      ' || RPAD(v_dname, 14) || ' ' ||
            v_loc);
    END LOOP;
    CLOSE emp_cursor;
END;

This program returns the following sample output:

EMPNO    ENAME     DEPTNO    DNAME          LOC
-----    -------   ------    ----------     ---------
7369     SMITH       20      Research       Dallas
7499     ALLEN       30      Sales          Chicago
7521     WARD        30      Sales          Chicago
7566     JONES       20      Research       Dallas
7654     MARTIN      30      Sales          Chicago
7698     BLAKE       30      Sales          Chicago
7782     CLARK       10      Accounting     New York
7788     SCOTT       20      Research       Dallas
7839     KING        10      Accounting     New York
7844     TURNER      30      Sales          Chicago
7876     ADAMS       20      Research       Dallas
7900     JAMES       30      Sales          Chicago
7902     FORD        20      Research       Dallas
7934     MILLER      10      Accounting     New York