mysql利用子查詢效率怎么樣

mysql子查詢效率：利用子查詢【SELECT id,`name` FROM customer where id IN(select DISTINCT(customerid) from searchaccount】效率是10倍級的影響。

mysql利用子查詢后的效率影響

僅僅是利用id:

explain  SELECT * from customer where id in(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20)

結果：

利用了子查詢：

explain  SELECT id,`name` FROM customer where id IN(select DISTINCT(customerid) from searchaccount WHERE kfuid=126 AND iskf=1) LIMIT 20

結果：

不用子查詢，達到同樣的效果：

explain  select DISTINCT(customerid) as id,c.name from searchaccount s LEFT JOIN customer c on s.customerid=c.id WHERE s.kfuid=126 AND s.iskf=1 limit 20

效率是10倍級的影響。

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