MySQL select rows where left join is null

Question

I have these MySQL tables:

table1:

id | writer
1  | Bob   
2  | Marley
3  | Michael

table2:

user_one | user_two
            


        

Answer 1

Try:

SELECT A.id FROM
(
  SELECT table1.id FROM table1 
  LEFT JOIN table2 ON table1.id = table2.user_one
  WHERE table2.user_one IS NULL
) A
JOIN (
  SELECT table1.id FROM table1 
  LEFT JOIN table2 ON table1.id = table2.user_two
  WHERE table2.user_two IS NULL
) B
ON A.id = B.id

See Demo

Or you could use two LEFT JOINS with aliases like:

SELECT table1.id FROM table1 
 LEFT JOIN table2 A ON table1.id = A.user_one
 LEFT JOIN table2 B ON table1.id = B.user_two
 WHERE A.user_one IS NULL
 AND B.user_two IS NULL

See 2nd Demo