Using joins correctly

Question

I am looking for a tip on how to optimize this....

SELECT   u.uid,
         u.username,
         u.nid,
         wd.pay
FROM     (users_data AS u
          LEFT JOIN winners_data wd
            ON u.nid = wd.nid
               AND u.uid = wd.uid)
         LEFT JOIN dp_node dn
           ON u.nid = dn.nid
WHERE    u.uid = ".$val."
         AND ((dn.TYPE = 'event'
               AND (SELECT Count(nid)
                    FROM   tournament_event
                    WHERE  nid = u.nid
                           AND type_value IN ('A','B','C')) > 0)
               OR (dn.TYPE = 'new_event'
                   AND (SELECT Count(nid)
                        FROM   user_tournament_event
                        WHERE  nid = u.nid
                               AND type_0_value IN ('Y','X')) > 0))
ORDER BY nid ASC

Actually the $val is nothing but the uid that comes from the following query one at a time as a part of my loop.

SELECT DISTINCT(dump.uid) FROM leader_Jdump AS dump

Is there any way to add this part as well to the above query? I guess it will be faster if I can do it at the MySQL level.

Answer 1

Try this:

SELECT  u.uid, u.username, u.nid, wd.pay
FROM    users_data AS u
LEFT JOIN
        winners_data wd
ON      (wd.nid, wd.uid) = (u.nid, u.uid)
JOIN    dp_node dn 
ON      dn.nid = u.nid
        AND dn.type IN ('event', 'new_event')
WHERE   u.uid = ".$val."
        AND EXISTS
        (
        SELECT  NULL
        FROM    tournament_event te
        WHERE   te.nid = u.nid
                AND type_value IN ('A', 'B', 'C')
                AND dn.type = 'event'
        UNION ALL
        SELECT  NULL
        FROM    user_tournament_event te
        WHERE   te.nid = u.nid
                AND type_0_value IN ('X', 'Y')
                AND dn.type = 'new_event'

        )
ORDER BY
        u.nid ASC

I removed OUTER JOIN from dp_node, since your original query required a non-NULL condition on a dp_node field in WHERE clause, so LEFT JOIN is useless here.

Create the following indexes:

users_data (uid, nid)
winners_data (uid, nid)
dp_node (nid, event_type)
tournament_event (nid, type_value)
user_tournament_event (nid, type_0_value)

Answer 2

This might be equivalent, but easier to read:

WITH NIDs(type_value,nid) AS (
  SELECT 'event', nid FROM tournament_event
  WHERE type_value IN ('A','B','C')
  UNION ALL
  SELECT 'new_event', nid FROM user_tournament_event
  WHERE type_value IN ('X','Y')
)

SELECT
  u.uid,
  u.username,
  u.nid,
  wd.pay
FROM users_data AS u JOIN NIDs AS n
ON n.nid = u.nid
AND n.type_value = u."type"
LEFT JOIN winners_data AS wd
ON u.nid=wd.nid AND u.uid=wd.uid
LEFT JOIN dp_node AS dn 
ON u.nid = dn.nid
WHERE u.uid=".$val."
ORDER BY nid ASC

If "what kind of event" is an important one, you would be better off with a single table from which you can make that determination by looking at a single column or two. You seem to have two tables holding this information (tournament_event and user_tournament_event). For example, you could store information as in the NIDs expression of this query.

Added on 2009-08-22:

Here's the same query, with the CTE expressed as a derived table:

SELECT
  u.uid,
  u.username,
  u.nid,
  wd.pay
FROM users_data AS u JOIN (
  SELECT 'event', nid FROM tournament_event
  WHERE type_value IN ('A','B','C')
  UNION ALL
  SELECT 'new_event', nid FROM user_tournament_event
  WHERE type_value IN ('X','Y')
) AS n(type_value,nid)
ON n.nid = u.nid
AND n.type_value = u."type"
LEFT JOIN winners_data AS wd
ON u.nid=wd.nid AND u.uid=wd.uid
LEFT JOIN dp_node AS dn 
ON u.nid = dn.nid
WHERE u.uid=".$val."
ORDER BY nid ASC

Answer 3

I've seen this style (all of the closing parenthesis at the end of a single line) and wonder how people can make sense of it. Someone asked earlier for a reformatted version:

SELECT    u.uid,
          u.username,
          u.nid,
          wd.pay
FROM      users_data u
          LEFT JOIN winners_data wd
               ON u.nid = wd.nid
               AND u.uid = wd.uid
          LEFT JOIN dp_node dn
               ON u.nid = dn.nid
WHERE     u.uid = ".$val."
          AND (
                (
                    dn.TYPE = 'event'
                    AND (
                        SELECT Count(nid)
                        FROM   tournament_event
                        WHERE  nid = u.nid
                               AND type_value IN ('A','B','C')
                    ) > 0
                )
                OR (
                    dn.TYPE = 'new_event'
                    AND (
                        SELECT Count(nid)
                        FROM   user_tournament_event
                        WHERE  nid = u.nid
                               AND type_0_value IN ('Y','X')
                    ) > 0
                )
          )
ORDER BY  nid ASC