Executes one of a sequence of alternate statement blocks in a
    compound statement of a multistatement procedure.

1  –  Environment

    You can use the simple CASE control statement in a compound
    statement of a multistatement procedure:

    o  In interactive SQL

    o  Embedded in host language programs to be precompiled

    o  As part of a procedure in an SQL module

    o  In dynamic SQL as a statement to be dynamically executed

2  –  Format

  case-statement =

  CASE value-expr --------+
  +-----------------------+
  ++-> WHEN -+-+> <literal> -+-+-> THEN -+-> compound-use-statement -+-+-+
   |         | +> NULL ------+ |         +------------<--------------+ | |
   |         +----- , <--------+                                       | |
   +---------------------------------<---------------------------------+ |
    +--------------------------------<-----------------------------------+
    ++----------------------------------------+--> END CASE --->
     +--> ELSE -+-> compound-use-statement -+-+
                +------------<--------------+

3  –  Arguments

3.1  –  CASE

    An expression that evaluates to a single value. SQL compares the
    CASE clause value expression with each WHEN clause literal value
    in the WHEN clauses until it finds a match.

    The value expression cannot contain a column specification that
    is not part of a column select expression.

    See the Value_Expressions HELP topic for a complete description
    of the variety of value expressions that SQL provides.

3.2  –  ELSE

    Executes a set of SQL statements when SQL cannot find a WHEN
    clause that matches the value expression in the CASE clause.

    See the Compound_Statement HELP topic for a description of the
    SQL statements that are valid in a compound statement.

3.3  –  THEN

    Executes the set of SQL statements associated with the first
    WHEN clause in which its argument value matches the CASE value
    expression.

3.4  –  WHEN

    Syntax options:

    WHEN literal | WHEN NULL

    The literal or NULL value of the WHEN clause that SQL compares
    with the value expression of the CASE clause. Most CASE control
    statements include a set of WHEN clauses.

    When the values of the WHEN and CASE clauses match, SQL executes
    the SQL statements associated with that WHEN clause. Control then
    drops out of the CASE control statement and returns to the next
    SQL statement after the END CASE clause.

4  –  Examples

    Example 1: Using the CASE control statement

    char x[11];
    long x_ind;
       EXEC SQL
          DECLARE ALIAS FOR FILENAME personnel ;

       EXEC SQL
          BEGIN
             CASE :x  INDICATOR :x_ind
                WHEN 'Abrams' THEN
                   DELETE FROM employees WHERE . . . ;
                WHEN NULL THEN
                   DELETE FROM employees WHERE . . . ;
                ELSE
                   DELETE FROM employees WHERE . . . ;
             END CASE ;
          END ;

    Example 2: Using a List of Literal Values with the Case Statement

    SQL> DECLARE :CODE CHAR(4);
    SQL> BEGIN
    cont>    JOB_LOOP:
    cont>        FOR :JOBFOR
    cont>          AS EACH ROW OF
    cont>          SELECT * FROM JOBS JOB
    cont>          DO
    cont>          SET :CODE = :jobfor.JOB_CODE;
    cont>            CASE :CODE
    cont>              WHEN 'ASCK' THEN
    cont>                 UPDATE JOBS
    cont>                 SET MINIMUM_SALARY=10000
    cont>                 WHERE JOB_CODE = :code;
    cont>              WHEN 'ADMN', 'JNTR', 'SCTR' THEN
    cont>                 UPDATE JOBS
    cont>                 SET MINIMUM_SALARY=15000
    cont>                 WHERE JOB_CODE = :code;
    cont>              ELSE
    cont>                 UPDATE JOBS
    cont>                 SET MINIMUM_SALARY=:jobfor.MINIMUM_SALARY*1.1
    cont>                 WHERE JOB_CODE=:code;
    cont>            END CASE;
    cont>        END FOR;
    cont> END;
    SQL>