Triggers that run after an update, insert, or delete can
be used in several ways.
- Triggers can update, insert, or delete data in the same or other
tables. This is useful to maintain relationships between data or to
keep audit trail information.
- Triggers can check data against values of data in the rest of
the table or in other tables. This is useful when you cannot use referential
integrity constraints or check constraints because of references to
data from other rows from this or other tables.
- Triggers can use user-defined functions to activate non-database
operations. This is useful, for example, for issuing alerts or updating
information outside the database.
Example
The following example presents
an AFTER trigger that increases the number of employees when a new
employee is hired.
CREATE TRIGGER NEW_HIRE
AFTER INSERT ON EMPLOYEE
FOR EACH ROW
UPDATE COMPANY_STATS SET NBEMP = NBEMP + 1
DB2 10.5 for Linux, UNIX, and Windows