mysql 排行榜函数

给重复的email按日期排序

SELECT   UserFormSubmit,Form_Submit_Date , pkid ,
@position := if(@previous = Email_Address, @position, 0) + 1 AS position  ,
@previous := Email_Address as email
FROM  vm_reg_info ,
( SELECT @previous := -1, @position := 0) AS s  

ORDER BY Email_Address,Form_Submit_Date,pkid;

update vm_reg_info r
left join tmp_table t
on r.Email_Address=t.email
set r.repeat_id=t.UserFormSubmit
where r.pkid!=t.pkid and t.position=1;