 <p>Trigger is not going to execute for each <code>Row</code>. Change your trigger like this. </p> <pre><code>CREATE TRIGGER trig_INVOICE ON INVOICE after INSERT, UPDATE AS BEGIN UPDATE a SET AMOUNT = QUANTUM * p.price FROM INVOICE a JOIN inserted b ON a.PRODUCTID = b.PRODUCTID JOIN PRODUCT p ON a.PRODUCTID = p.PRODUCTID END </code></pre>