Question

Is it possible to write a sql query where you know you have to use the left outer join..but cannot or are not allowed to use the “outer join” Key Word

I have two table sand want to get rows with null vaues from the left table …this is pretty simple …but am not supposed to use the key word….outer join….I need to right the logic for outer join myself

Answer 1

SELECT Field1 
FROM table1 
WHERE id NOT IN (SELECT id FROM table2)

SELECT Field1 
FROM table1 
WHERE NOT EXISTS (SELECT * FROM table2 where table2.id = table1.id)

This is something people do but it is deprecated and it does not currently work correctly (it sometimes will return a cross join instead of a left join) so it should NOT be used. I’m telling this only so you avoid using this solution.

SELECT Field1 
FROM table1, table2 where table1.id *= table2.id