But if the case is different like
Table A Table B
Invoice Number Inventory Number Inventory Number
101 100001 100001
101 100002 100002
102 100001 100003
Note: Inventory Number in Table A is inserting from Table B by using a script.
Now, I want to prevent the duplicate entry that in Table A, if invoice number 101 has the inventory number 100002 don't get an insert it from Table B.
I think unique value validation will not work in this case. Looking for the suggestions.