Writing UNION statements in MySQL 3.x
Posted on 12月 12th, 2007 作者 哈哈
mysql里，从4.0开始支持UNION语句
用来把不同的结果集合成一个
今天需要写个SQL语句
用UNION会非常简单，但是数据库是3.23的
于是就想3.x的mysql怎样替代union呢
于是去网上搜，还真找到了
看Writing UNION statements in MySQL 3.x
这里，有点拿不准的就是表_dummy
直接用会发现说_dummy这个表找不到的错误
最后手工建了个表_dummy
还添加了2条记录：“0”、“1”
然后就搞定了
SELECT DISTINCT
IFNULL(d1.t1.ip, d2.t2.tsip) AS ip,
IFNULL(d1.t1.port, d2.t2.tsport) AS port,
IFNULL(d1.t1.cguid, d2.t2.channelid) AS cguid
FROM _dummy AS d
LEFT JOIN d1.t1
ON (d.num = 0
AND d1.t1.ip is not null
AND d1.t1.port > 0
AND d1.t1.tport > 0)
LEFT JOIN d2.t2
ON (d.num = 1
AND d2.t2.tsport > 0
AND d2.t2.tsip != ”
AND d2.t2.tsip is not null
AND d2.t2.channelid != ”
AND d2.t2.channelid is not null)
WHERE d.num < 2
ORDER BY ip, port
