Not exactly sure what you mean, but you can exclude certain values using a subquery and either the "IN" operator or the "=" operator:
SELECT ID1, SomeCol FROM Table1
WHERE ID1 NOT IN (SELECT ID2 FROM Table2)
You could put where conditions on the subquery if you want. You could also make the subquery be for the same table. For example:
SELECT ID1, SomeCol FROM Table1 WHERE ID1 NOT IN
(SELECT T.ID1 FROM Table1 AS T WHERE T.SomeCol = 'SomeVal')