select

from

where

grouo by分組

having分組在篩選

order by排序

select shb ，count(*)

from zx_student

where (xb='nan')

group by shb 按照班級(jí)分組

having count(*) > 50 分組進(jìn)行篩選

order by 2

select *

from zx_student

where xm in (

select xm

from zx_student

group by xm

having count(*) > 1)

order by xm