有两个表：SPEC1、tmpDOT SPEC1种一列为：HIGH tmpDOT共有两个：OLD、NEW 两个表的内容大概如下： SPEC1: ... HIGH ... ... A    ... ... B    ... ... A    ... ... C    ... ... B    ... ... D    ... tmpDOT： OLD   NEW A     newA B     newB

C     newC

方法一

update a setHIGH=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 newON 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 whereold=a.high  )

from spec1 a