mysql分组排名

关联一个 ( SELECT @id := 0 ) idVal，用逗号就行，或者用join 且要嵌套多层

 select t2.* from (
             select
              ( @id := @id + 1 ) AS id,
              t.* from (
                    SELECT
                        COUNT( act.visit_no ) rankCount,
                        act.nameFROM
                        activity_clock_type act                      
WHERE
                        act.activity_no = #{activityNo}
                    GROUP BY
                        act.staff_no
                    ORDER BY
                        rankCount DESC , act.create_time asc
                ) t ,  ( SELECT @id := 0 ) idVal
            ) t2