Statement Level Trigger

CREATE TRIGGER average-price-preserve

INSTEAD OF UPDATE OF price ON Product

REFERENCING

OLD_TABLE AS OldStuff (the old versions of the tuples)

NEW_TABLE AS NewStuff (the new versions)

WHEN (1000 <

(SELECT AVG (price)

FROM ((Product EXCEPT OldStuff) UNION NewStuff))

DELETE FROM Product

WHERE (name, price, company) IN OldStuff;

INSERT INTO Product

(SELECT * FROM NewStuff)