how to avoid duplicate insert in a table? I use below query to insert in to table: insert into RefundDetails(ID,StatusModified,RefundAmount,OrderNumber) select O.id,O.StatusModified,OI.RefundAmount,O.OrderNumber from Monsoon.dbo.[Order] as O WITH (NOLOCK) JOIN Monsoon.dbo.OrderItem as OI WITH (NOLOCK)on O.Id = OI.OrderId WHERE o.ID in (SELECT OrderID FROM Mon2QB.dbo.monQB_OrderActivityView WHERE ACTIVITYTYPE = 4 AND at BETWEEN '10/30/2012' AND '11/3/2012') AND (O.StatusModified < '11/3/2012')