数据库_基础知识_MySQL_UpdateSelect(根据查询出来的结果批量更新)

样例有两个表：spec1、tmpdot
spec1 表 有一列：high 
tmpdot 表 共有两个列：old、new
两个表的内容大概如下：
 

spec1 表:

tmpdot 表：

方法一

UPDATE a SET high = b.new
FROM spec1 a, tmpdot  b   
WHERE a.high=b.old  

方法二

UPDATE a
SET high = b.new  
FROM a LEFT JOIN b ON ( a.high = b.old )  

一个复杂的栗子：一个更新多个字段的例子

UPDATE a JOIN b ON a.XX= b.XX

SET a.Y = b.Y,   a.Z = b.Z

-- 正式版本 最终版 统计上班排名和时间
	UPDATE mobile_user_total AS old 
	INNER JOIN 
		(
			SELECT u_info.user_id, class.class_name, u_info.`name`, a.clock_date AS arrive_time, COUNT(b.user_id)+1 AS up_rank
			FROM user_info u_info 
			JOIN user_class u_class ON u_info.user_id = u_class.user_id
			JOIN class ON class.id = u_class.class_id
			JOIN 
					# a 表作为考勤主表用来统计用户没有迟到的最早记录
					(
					SELECT u_clock.user_id, MIN(clock_date) AS clock_date, u_class.class_id
					FROM user_clockrecords u_clock
					JOIN user_class u_class ON u_class.user_id = u_clock.user_id
					JOIN class ON u_class.class_id = class.id
					WHERE DATE(clock_date) = cal_date AND DATE_FORMAT(u_clock.clock_date,'%H:%i:%s') < DATE_FORMAT(class.begin_time,'%H:%i:%s')	#根据传入的日期
					GROUP BY user_id
					)AS a ON u_info.user_id = a.user_id	
					LEFT JOIN(
					SELECT u_clock.user_id, MIN(clock_date) AS clock_date, u_class.class_id
					FROM user_clockrecords u_clock
					JOIN user_class u_class ON u_class.user_id = u_clock.user_id
					JOIN class ON u_class.class_id = class.id
					WHERE DATE(clock_date) = cal_date AND DATE_FORMAT(u_clock.clock_date,'%H:%i:%s') < DATE_FORMAT(class.begin_time,'%H:%i:%s')	#根据传入的日期
				GROUP BY user_id
				)AS b ON a.class_id = b.class_id AND u_info.user_id <> b.user_id AND b.clock_date < a.clock_date
			GROUP BY u_info.user_id
		)AS new	ON old.user_id = new.user_id AND old.`current_time` = cal_date		#根据传入的日期
	SET old.work_clock_time = new.arrive_time, old.up_ranking = new.up_rank;

方法三

UPDATE  a  
SET high  = ( SELECT new FROM tmpdot WHERE old = a.high  )  
FROM spec1 a