MySQL：每个INNER JOIN的条件不同

Question

I have the following mysql query

SELECT n.* FROM notifications as n
  INNER JOIN notifications as nc ON ...  ...
     INNER JOIN following as f ON ...  ...
         WHERE
           (condition 1)
                OR
                  (condition 2)

My guestion is how i can make sure that condition 1 is evaluted for the first inner join (nc) and condition 2 is evaluted for the second inner join (f)

Answer 1

The best way is to move you conditions from WHERE clause to ON clause. In case on Inner Join, WHERE and ON work in same manner and it is always better to filter out data as early as possibly in the query. So, your query will look like: SELECT n.* FROM notifications as n INNER JOIN notifications as nc ON ... ... AND (Condition 1) INNER JOIN following as f ON ... ... AND (Condition 2)