需求:
根據同一表的某條件更新欄位

情況一: 以group by 作為條件的

select user a, (select count(*) as tj_num, s_id from user group by s_id) b set a.tuijian_num=b.tj_num where a.id=b.s_id; 

情況二: 不能以group by 作為條件的

#呼叫方法：call proc_update_team_info();
DELIMITER ;;
CREATE  PROCEDURE `proc_update_team_info`()
BEGIN   
    DECLARE done tinyint default 0;
    DECLARE uid int(11);
    DECLARE team_num int DEFAULT 0;
    DECLARE user_tree text DEFAULT '';
    DECLARE cs CURSOR FOR SELECT id FROM `user` order by id asc;
    DECLARE continue handler for sqlstate '02000' set done=1;
    open cs;
    while done<>1 do
    fetch cs into uid;
        select CONCAT(s_tree,id,',%') INTO user_tree  from `user` where id=uid;
        select user_tree;
        select if(count(*) is null,0,count(*)) into team_num  from `user` where s_tree like(user_tree);
        update `user` set team_num=team_num where id=uid;
    end while;
    close cs;   
END
;;
DELIMITER ;