mysql 奇淫巧技(慢慢補充~)

1. sql內使用變量

select  roleid,id, IF(@pre=roleid,@rownum:=@rownum+1,@rownum:=1) as rownum ,@pre:=roleid
from (
	select  a.roleid, a.id  from login a,
	(SELECT  DISTINCT(roleid) from login where  generatetime >= '2019-03-01' and generatetime<'2019-03-02') b
	where  a.roleid=b.roleid GROUP BY a.roleid ,a.id order by a.id  
) ret,(select @pre:='',@rownum:=0 ) numgen   order by roleid