Question

I am trying to do a query with an outer join, and I’ve always used Oracle Pl/SQL in the past, but am now trying to learn MySQL. I’m trying to join 3 tables, USERS, USER_TYPE, and GRADE. The USERS table contains column, USER_TYPE_ID, which is a foreign key to USER_TYPE, and it also contains column, GRADE_ID which is a foreign key to GRADE. I need the outer join because user types could be student, faculty, etc, and if it is a faculty member then the USER does not have a grade, hence a NULL GRADE_ID in the USER table. Here is what my query would have looked like in the past using (+) for the outer join.

SELECT A.USER_NAME
     , A.USER_TYPE_ID
     , B.USER_TYPE_DESC
     , A.GRADE_ID
     , C.GRADE_DESC
  FROM USERS A
     , USER_TYPE B
     , GRADE C
 WHERE A.USER_TYPE_ID = B.USER_TYPE_ID
   AND A.GRADE_ID = C.GRADE_ID (+);

Could someone please help me translate this into a MySQL query?

Thanks in advance!

Answer 1

SELECT u.user_name, u.user_type_id, ut.user_type_desc, u.grade_id, g.grade_desc
FROM users u JOIN user_type ut ON (ut.user_type_id = u.user_type_id)
LEFT JOIN grade g ON (u.grade_id = g.grade_id);