讲id为8的记录的nick的值复制到id为9的记录里面
UPDATE userinfo SET nick = (SELECT t.nick from (SELECT tmp.* FROM userinfo tmp WHERE id = 8) t) WHERE id = 9讲id为8的记录的nick的值复制到id为9的记录里面
UPDATE userinfo SET nick = (SELECT t.nick from (SELECT tmp.* FROM userinfo tmp WHERE id = 8) t) WHERE id = 9