MySQL的左連接查詢優化

-1

SELECT P.*, COUNT(L.to) AS likes, U.name AS ownerName, U.username AS ownerUsername, 
    U.picture AS ownerPicture 
FROM sn_posts P LEFT JOIN sn_users AS U 
    ON U.id = P.ownerID 
LEFT JOIN sn_likes AS L 
    ON L.to = P.id 
WHERE (P.ownerID = 69) 
GROUP BY P.id 
ORDER BY P.id DESC

它採取 - 0.3337秒的時間，

來源

2016-07-07 Gkts App

我想優化我上面查詢.. –

你好，歡迎來到SO--請儘量提供更多信息 - 表格結構，數據量，指標等 - 所以人們實際上有辦法幫助你。 –

您可以將索引添加到聯接列中，除此之外，您的查詢對我來說確實很好。 –

爲表sn_posts添加一個索引與ownerID場可以是更好

來源

2016-07-07 06:36:24 Joker

已經在ownerID上索引，但結果是顯示行0-10（總計11個，查詢花了0.3854秒） –

試試這個：SELECT P. *，COUNT（L.to）AS贊，U.name AS ownerName，U.username AS ownerUsername， U.picture AS ownerPicture FROM sn_posts P LEFT JOIN爲u sn_users ON U.id = P.ownerID AND P.ownerID = 69 LEFT JOIN sn_likes爲L ON L.to = P.id GROUP BY P.id ORDER BY P.id DESC – Joker

錯誤的結果... –

MySQL的左連接查詢優化

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