SQL Select where two values not in the same row of another table

Question

I need a select that return the values from T2.C from rows which combination of T2.A and T2.B doesn't exist in T1.

Something like:

select C from T2 where A,B not in (select A,B from T1)

Results from example must be:

C
--
y
z

Answer 1

Do you mean like

SELECT T2.*
FROM T2
LEFT OUTER JOIN T1
 ON T2.ColumnA = T1.ColumnA
 AND T2.ColumnB = T1.ColumnB
WHERE T1.ColumnA IS NULL;

If you do an outer join, you can easily notice a lack of a match (via nulls).