mysql实现row_number() 功能

查询test表按group_id分组取sort_id前100个

SELECT id AS '原数据ID',group_id AS '分组ID',sort_id AS '排序条件',num AS '排名'
FROM 
    (SELECT  @row_number := CASE WHEN  @customer_no = group_id  THEN  @row_number + 1  ELSE  1 END   AS  num /*如果同group_id那么排名加1,否则更新为1*/
    ,@customer_no := group_id  AS  group_id /*重新加载group_id*/
    ,id , sort_id /*原有数据*/
 FROM  test,( SELECT  @customer_no := 0,@row_number := 0)  AS  t
 ORDER BY group_id ,sort_id DESC ,id)a 
WHERE num<=100