Question

What I’m trying to do is return all the records my persons table that do not exist in secondary table or that do exist, but only if one they have null values in one of two specific fields. So given the following tables

person_id   ....
----------------
123         ....
456         ....
789         ....

p_id    colA    colB
--------------------
456     aadl
789     023j    ljlj

I would get back the following

person_id   ....
----------------
123         ....
456         ....

This would be because person 123 does not exist in the secondary table. Person 456 would also be returned because they exist, but one of the two columns are null.

Thanks!

Answer 1

You could write:

SELECT *
  FROM persons
 WHERE person_id NOT IN
        ( SELECT p_id
            FROM secondary_table
           WHERE colA IS NOT NULL
             AND colB IS NOT NULL
        )
;