mysql - Sql union 操作
本文介绍了mysql - Sql union 操作的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
问 题
问题:
第一种写法:
(select du.day,du.apptoken ,du.version, du.channel,du.city,du.count,concat(apptoken,
version,channel,city) as joinkey from day_new_users_count du where day='20170319') as dayUsers
union
(select tu.day,tu.apptoken,tu.version,tu.channel,tu.city,tu.count,concat(apptoken,version,channel,city) as joinkey from total_users tu where day='20170318') as toUsers
第二种写法:
select du.day,du.apptoken ,du.version, du.channel,du.city,du.count,concat(apptoken, version,channel,city) as joinkey from day_new_users_count du where day='20170319'
union
select tu.day,tu.apptoken,tu.version,tu.channel,tu.city,tu.count,concat(apptoken,version,channel,city) as joinkey from total_users tu where day='20170318'
为什么第二种写法可以正确执行,第一种方式就不可以??
区别 不是 第一种方式中给 临时表起了个别名嘛,怎么就不行了?高人指点呐
解决方案
select * from (
select
du.day, du.apptoken , du.version, du.channel, du.city, du.count,
concat(apptoken, version,channel,city) as joinkey
from day_new_users_count du
where day='20170319'
) as dayUsers
union
select * from (
select
tu.day, tu.apptoken, tu.version, tu.channel, tu.city, tu.count,
concat(apptoken,version,channel,city) as joinkey
from total_users tu
where day='20170318'
) as toUsers
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