mysql子查询效率:利用子查询【SELECT id,`name` FROM customer where id IN(select DISTINCT(customerid) from searchaccount】效率是10倍级的影响。 mysql利用子查询后的效率影响 仅仅是利用id: explain SELECT * fr
mysql子查询效率:利用子查询【SELECT id,`name` FROM customer where id IN(select DISTINCT(customerid) from searchaccount】效率是10倍级的影响。
mysql利用子查询后的效率影响
仅仅是利用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)
结果:
利用了子查询:
explain SELECT id,`name` FROM customer where id IN(select DISTINCT(customerid) from searchaccount WHERE kfuid=126 AND iskf=1) LIMIT 20
结果:
不用子查询,达到同样的效果:
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倍级的影响。
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