我现在有三个表 conference表，time1表，time2表
conference表有 conference_id ,conference_name
time1表有 conference_id,time1（时间类型）
time2表有conference_id,time2（时间类型）
我想通过conference_id得到time1，time2表中最大的时间，我这么写sql，但是不行
SELECT CONFERENCE_NAME,
(SELECT MAX(MAX_TIME)
FROM (SELECT TIME1 MAX_TIME
FROM TIME1 T1
WHERE T1.CONFERENCE_ID = C.CONFERENCE_ID
UNION
SELECT TIME2 MAX_TIME
FROM TIME2 T2
WHERE T2.CONFERENCE_ID = C.CONFERENCE_ID)) MAX_TIME
FROM CONFERENCE C
报c.conference_id标识符无效，求大家帮助，谢谢
------解决方案--------------------
- SQL code
--試下select c.conference_id,t1.time1,t2.time2from conference cleft join (select max(time1) time1 from time1 group by conference_id) t1 on c.conference_id=t1.conference_idleft join (select max(time2) time2 from time2 group by conference_id) t2 on c.conference_id=t2.conference_id
------解决方案--------------------
- SQL code
--1、union 本身就能剔重SELECT CONFERENCE_NAME, (SELECT MAX(TIME1) FROM TIME1 T1 WHERE T1.CONFERENCE_ID = C.CONFERENCE_ID UNION SELECT MAX(TIME2) FROM TIME2 T2 WHERE T2.CONFERENCE_ID = C.CONFERENCE_ID) MAX_TIME FROM CONFERENCE C--2、用分析函数来做SELECT CONFERENCE_NAME, GREATEST(MAX(T1.TIME1) OVER(), MAX(T2.TIME2) OVER()) MAX_TIME FROM CONFERENCE C, TIME1 T1, TIME2 T2 WHERE T1.CONFERENCE_ID = C.CONFERENCE_ID AND T2.CONFERENCE_ID = C.CONFERENCE_ID;