為多個列優化mysql子查詢

Question

我有一個節目表，里面有250萬條記錄。 節目表中的列是id，showid，artist_id，cityid，已創建。

如果同一場演出正在進行4天。 然后在系統中的數據將像：

為每個節目創建的ID，ShowID，Artist_ID，CityID，ShowID將保持不變。

1 245 1 3 2011-12-30 15:00:00

2 245 1 3 2011-12-30 13:00:00

3 245 1 3 2011-12-30 19:00:00

SELECT UT.user_id,UT.type_id, UT.type ,UT.track_time, 
(SELECT showid FROM shows WHERE FIND_IN_SET(UT.type_id,artist_id) ORDER BY created DESC LIMIT 1)   as mainshowid,
(SELECT cityid FROM shows WHERE FIND_IN_SET(UT.type_id,artist_id) ORDER BY created DESC LIMIT 1)   as maincityid
FROM user_details as UT  WHERE UT.type='artist' ORDER BY UT.track_time desc limit 20;

查詢提供了期望的輸出，但是我如何在單個SUB查詢中或通過任何其他方式獲取多列。

Answer 1

您可以：

SELECT 
    UT.user_id,
    UT.type_id, 
    UT.type,
    UT.track_time, 
    s.showid AS mainshowid,
    s.cityid AS maincityid
FROM 
      user_details AS UT 
  JOIN
      shows AS s
    ON s.showid =
       ( SELECT showid 
         FROM shows 
         WHERE FIND_IN_SET(UT.type_id, artist_id)
         ORDER BY created DESC 
         LIMIT 1
       ) 
WHERE UT.type='artist' 
ORDER BY UT.track_time DESC 
LIMIT 20 ;