Database two table ABs in the same structure or the similar structure to see the anti-set of A-B / A n b / (a n b)
Example: Tables A and Table B have only one field TEL.
(A - b)
Select * from a left join b on a.tel = b.tel where b.tel is null
(A n b)
Select * from a left join b on a.tel = b.tel where b.tel is not null
Anti-set of (a n b)
SELECT T1.TEL AS TELA, T2.TEL from T1 Right Join T2 on T1.TEL = T2.TEL WHERE T1.TEL IS NULL
