2
有什麼方法可以更快地優化此查詢？查詢優化
SELECT id FROM business
WHERE id NOT IN(SELECT business_id FROM business_community GROUP BY business_id)
Q
查詢優化
A
回答
5
試試這個：
SELECT id FROM business AS b
LEFT JOIN business_community bc ON bc.business_id = b.id
WHERE bc.business_id IS NULL
+0
這工作得很好。 。 謝謝 – gumpi 2010-12-10 16:00:33
0
也許用 「DISTINCT business_id」，而不是一組由..
我不知道，如果一個LEFT JOIN後跟一個'NULL'檢查會更快，但我認爲這值得嘗試。 – lijie 2010-12-10 14:25:57
僅供參考，它是一個在mysql中的錯誤 - > http://stackoverflow.com/questions/3417074/why-would-an-in-condition-be-slower-than-in-sql – 2010-12-10 14:37:00