Quoth Jim Mellander <[email protected]>, on 2010-10-01 14:38:03 -0700:
> Hi:
>
> I want to use to trigger on deletion of a detail record to
> automatically delete a summary record, if not more detail records
> exist, something like:
>
> CREATE TRIGGER detail_delete AFTER DELETE ON detail
> BEGIN
> -- here I don't know syntax
> IF COUNT(detail records with key) = 0 DELETE summary WHERE key=old.key;
> END;
SQLite triggers don't use an imperative language with full control
structures, just basic SQL. However, in this case you can use a WHEN
clause:
CREATE TRIGGER auto_delete_summary AFTER DELETE ON detail
FOR EACH ROW WHEN NOT EXISTS (SELECT * FROM detail WHERE key = OLD.key)
BEGIN
DELETE FROM summary WHERE key = OLD.key;
END;
---> Drake Wilson
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