mysql查询优化问题

Question

select * from (select * from status where 1=1 ".$sch_q." order by stime desc ) as tmp where 1=1 ".$sch_s." group by name

'select * from (select * from (select * from status where 1=1 '.$sch_q.' order by stime desc ) as tmp group by name) as tmpp where status in (0,1,2,3)'.$sch_s

像这种select子查询该怎么优化 有谁可以帮帮忙吗？ 万分感谢！！！

注：

$sch_q = ' ';
$sch_s = ' ';

Answer 1

你的这个sql真的能运行么？ 第一层子查询里 group by name ,那么查询字段也只能是name或者聚合字段，select * 应该会报错的。

Answer 2

打开mysql query_cache

Answer 3

如果需要优化查询语句，最好先用explain 测试一下，然后看相关的参数进行优化。