SET transition-variable

The SET transition-variable statement assigns values to new transition-variables.

Invocation

This statement can only be used as an SQL statement in a BEFORE trigger. It is an executable statement that cannot be dynamically prepared.

Authorization

If a row-fullselect is specified, see fullselect for an explanation of the authorization required for each subselect.

Syntax

        .-,-------------------------------------------------------------------------.
        V                                                                           |
>>-SET----+-transition-variable-- = --+-expression-+------------------------------+-+-><
          |                           +-NULL-------+                              |
          |                           '-DEFAULT----'                              |
          |    .-,-------------------.               .-,--------------.           |
          |    V                     |               V                | (1)       |
          '-(----transition-variable-+--)-- = --(--+---+-expression-+-+------+--)-'
                                                   |   +-NULL-------+        |
                                                   |   '-DEFAULT----'        |
                                                   |                (2)      |
                                                   '-row-fullselect----------'
 

Description

transition-variable

Identifies the column to be updated in the new row. A transition-variable must identify a column in the subject table of a trigger, optionally qualified by a correlation name that identifies the new value. An OLD transition-variable must not be identified.

A transition-variable must not be identified more than once in the same SET transition-variable statement.

The data type of each transition-variable must be compatible with its corresponding result column. Values are assigned to transition-variables according to the assignment rules to a column. For more information see Assignments and comparisons.

expression

Specifies the new value of the transition-variable. The expression is any expression of the type described in Expressions. The expression cannot include an aggregate function.

An expression may contain references to OLD and NEW transition-variables. If the CREATE TRIGGER statement contains both OLD and NEW clauses, references to transition-variables must be qualified by the correlation-name.

NULL

Specifies the null value. NULL can only be specified for nullable columns.

DEFAULT

Specifies that the default value of the column associated with the transition-variable will be used. DEFAULT is not allowed if the column is an IDENTITY column or has a ROWID data type.

row-fullselect

A fullselect that returns a single result row. The result column values are assigned to each corresponding transition-variable. If the result of the fullselect is no rows, then null values are assigned. An error is returned if there is more than one row in the result.

Notes

Multiple assignments

If more than one assignment is included in the same SET transition-variable statement, all expressions are evaluated before the assignments are performed. Thus, references to transition-variables in an expression are always the value of the transition-variable prior to any assignment in the single SET statement.

Examples

Example 1: Ensure that the salary column is never greater than 50000. If the new value is greater than 50000, set it to 50000.

CREATE TRIGGER LIMIT_SALARY
  BEFORE INSERT ON EMPLOYEE
  REFERENCING NEW AS NEW_VAR
  FOR EACH ROW MODE DB2SQL
  WHEN (NEW_VAR.SALARY > 50000)
    BEGIN ATOMIC
    SET NEW_VAR.SALARY = 50000;
  END 

Example 2: When the job title is updated, increase the salary based on the new job title. Assign the years in the position to 0.

CREATE TRIGGER SET_SALARY
  BEFORE UPDATE OF JOB ON STAFF
  REFERENCING OLD AS OLD_VAR
              NEW AS NEW_VAR
  FOR EACH ROW MODE DB2SQL
  BEGIN ATOMIC
    SET (NEW_VAR.SALARY, NEW_VAR.YEARS) =
        (OLD_VAR.SALARY * CASE NEW_VAR.JOB
            WHEN 'Sales' THEN 1.1
            WHEN 'Mgr'   THEN 1.05
            ELSE 1 END ,0);
  END