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。