Databases Reference
In-Depth Information
DELIMITER $$
CREATE TRIGGER UpdateOrderLine
AFTER UPDATE ON OrderLine
FOR EACH ROW
BEGIN
UPDATE PART
SET OnOrder = OnOrder + New.NumOrdered - Old.NumOrdered
WHERE Part.PartNum = New.PartNum ;
END
$$
DELIMITER ;
The following DeleteOrderLine trigger performs a function similar to the other two. When an order line
is deleted, the OnOrder value for the corresponding part is updated by subtracting Old.NumOrdered from the
current OnOrder value. (In a delete operation, there is no New.NumOrdered.)
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DELIMITER $$
CREATE TRIGGER DeleteOrderLine
AFTER DELETE ON OrderLine
FOR EACH ROW
BEGIN
UPDATE PART
SET OnOrder = OnOrder - Old.NumOrdered
WHERE PartNum = Old.PartNum ;
END
$$
DELIMITER ;
Access does not support triggers. When using a form to update table data, you can achieve some of the
same funtionality by creating VBA code to be executed after the insertion, update, or deletion of records.
