Firebird 2.1 Language Reference Update

Multi-action triggers
Added in: 1.5
DDL statements
Description: Relation triggers can be defined to fire upon multiple operations (INSERT and/or UPDATE and/or
DELETE). Three new boolean context variables (INSERTING, UPDATING and DELETING) have been added so
you can execute code conditionally within the trigger body depending on the type of operation.
Example:
create trigger biu_parts for parts
before insert or update
as
begin
/* conditional code when inserting: */
if (inserting and new.id is null)
then new.id = gen_id(gen_partrec_id, 1);
/* common code: */
new.partname_upper = upper(new.partname);
end
Note
In multi-action triggers, both context variables OLD and NEW are always available. If you use them in the
wrong situation (i.e. OLD while inserting or NEW while deleting), the following happens:
• If you try to read their field values, NULL is returned.
• If you try to assign values to them, a runtime exception is thrown.
BEGIN ... END blocks may be empty
Changed in: 1.5
Description: BEGIN ... END blocks may be empty in Firebird 1.5 and up, allowing you to write stub code without
having to resort to dummy statements.
Example:
create trigger bi_atable for atable
active before insert position 0
as
begin
end
CREATE TRIGGER no longer increments table change count
Changed in: 1.0
Description: In contrast to InterBase, Firebird does not increment the metadata change counter of the associated
table when CREATE, ALTER or DROP TRIGGER is used. For a full discussion, see ALTER TRIGGER no longer
increments table change count.
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