自己解决了,用了UNION,不过只有4.0.0以上版本才支持(
SELECT privatemessage.title, privatemessage.receiveuser, privatemessage.sendtime, privatemessage.isread
FROM privatemessage
WHERE receiveuser = 'rainman'
)
UNION
(
SELECT privatemessage.title, multiplemessage.receiveuser, privatemessage.sendtime, multiplemessage.isread
FROM privatemessage, multiplemessage
WHERE multiplemessage.receiveuser = 'rainman' AND multiplemessage.messageid = privatemessage.messageid
)
ORDER BY privatemessage.sendtime
SELECT privatemessage.title, privatemessage.receiveuser, privatemessage.sendtime, privatemessage.isread
FROM privatemessage
WHERE receiveuser = 'rainman'
)
UNION
(
SELECT privatemessage.title, multiplemessage.receiveuser, privatemessage.sendtime, multiplemessage.isread
FROM privatemessage, multiplemessage
WHERE multiplemessage.receiveuser = 'rainman' AND multiplemessage.messageid = privatemessage.messageid
)
ORDER BY privatemessage.sendtime
要想不用union...思考中...
select sum(price) from tmp;
drop table tmp;