how to improve performance of update query in sql? -

I want to improve the performance of this update query because when it takes a lot of time to execute:

  Qry = "update tab 1 set cDate = GetDate () where correct ('000000000000' + in_num, 12) = '" & amp; InvNo.PadLeft (12, "0") & amp; "'And (total-amount) << Balance and cd is empty"  

Why are force-padding in_num and InvNo with major 0s with you:

  correct ('000000000000' + in_num , 12) = InvNo.PadLeft (12, "0")  

This will prevent any index from being used in in_num .