GEN ID( )

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Produces a system-generated integer value. Available in gpre, DSQL, and isql.

gen_id (generator, step)
Argument Description

<generator>

Name of an existing generator

<step>

Integer or expression specifying the increment for increasing or decreasing the current generator value. Values can range from –(263) to 263 – 1

Description: The GEN_ID() function:

  1. Increments the current value of the specified generator by step.
  2. Returns the new value of the specified generator.

GEN_ID() is useful for automatically producing unique values that can be inserted into a UNIQUE or PRIMARY KEY column. To insert a generated number in a column, write a trigger, procedure, or SQL statement that calls GEN_ID().

Note: A generator is initially created with CREATE GENERATOR. By default, the value of a generator begins at zero. It can be set to a different value with SET GENERATOR.

Examples: The following isql trigger definition includes a call to GEN_ID():

CREATE TRIGGER CREATE_EMPNO FOR EMPLOYEES
BEFORE INSERT
POSITION 0
AS BEGIN
NEW.EMPNO = GEN_ID (EMPNO_GEN, 1);
END

The first time the trigger fires, NEW.EMPNO is set to 1. Each subsequent firing increments NEW.EMPNO by 1.

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