MySQL Left Join not returning null values for joined table

Question

Please help me with the following MySQL query, which joins two tables (A and B):

SELECT * from A
left join B on A.sid = B.sid
where (rCode = 1 Or rCode = 2 O         


        

Answer 1

You should not specify rYear in a WHERE clause. Those limit your results after the join. You should specify rYear in an ON clause to get back records with NULL from table B.

SELECT * from A
left join B 
on A.sid = B.sid 
AND (rYear = 2011 or rYear is null)
where (rCode = 1 Or rCode = 2 Or rCode = 3 Or rCode = 5)