mysql分组用法

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--select num from 表 group by num --select num from 表 group by num,nid     --特别的：group by 必须在where之后，order by之前 --select num,nid from 表  where nid > 10 group by num,nid order by nid desc     -- group by是关键 -- 可接多个分组的判断条件 --select num,nid,count(*),sum(score),max(score),min(score) from 表 group by num,nid     --select num from 表 group by num having max(id) > 10