mysql 如何将行数插入到数据库

需求：MINGPIN_ACTIVITY 与 MINGPIN_ACTIVITY_SCORE 通过id关联，MINGPIN_ACTIVITY 有个fixed_position 字段，fixed_position 字段的顺序会被前台改动，

          要求按MINGPIN_ACTIVITY_SCORE 按score排序后将其行号同步到MINGPIN_ACTIVITY 的fixed_position 字段中

SQL语句：

UPDATE   MINGPIN_ACTIVITY b   (SELECT     @rownum := @rownum + 1 AS rownum,    activity_id   FROM    MINGPIN_ACTIVITY_SCORE mas,    (SELECT       @rownum := 0) t   WHERE mas.weight_id = - 1   ORDER BY score ASC) a SET  b.fixed_position = a.rownum WHERE b.id = a.activity_id