Update query no form numbers in second table

Question

I need to write an Oracle update query to set a reject flag on one table when the Form Number in the second table has all record equal to null.

Update Table1
set reject = 1

where Table2 has all records where the Form Number = null

I am not a SQL expert and I have to figure this out. I do not know if I use a Select or Join or what.

I would appreciate any help I can get.
Thanks,
arep

A Repasky · Answer

Here is the correct answer to this problem arep: UPDATE Table1 SET Reject = 1 WHERE FormN in (SELECT DISTINCT Table1.FormN FROM Table1 left outer join Table2 on Table1.FORMN = Table2.formn WHERE Table2.FormN is null)

A Repasky · Answer

Will this work? arep UPDATE HENCNP SET Reject = 1 WHERE FormN in (SELECT DISTINCT FormN FROM HENCDP WHERE FormN is null)