sql语句查询结果合并union all用法

sql语句查询结果合并union all用法2007-05-31 动态网站制作指南整理别人的sql

大概的思想是用union 和union all

--合并重复行
select * from A
union
select * from B

--不合并重复行
select * from A
union all
select * from B

按某个字段排序
--合并重复行
select *
from （
select * from A
union
select * from B） AS T
order by 字段名

--不合并重复行
select *
from （
select * from A
union all
select * from B） AS T
order by 字段名

//sql server版
Select * From （
select top 2 id,adddate,title,url from bArticle where ClassId="1" order by adddate desc） A
Union All
Select * From （
select top 2 id,adddate,title,url from bArticle where ClassId="2" order by adddate desc） B
Union All
Select * From （
select top 2 id,adddate,title,url from bArticle where ClassId="3" order by adddate desc） C
Union All
Select * From （
select top 2 id,adddate,title,url from bArticle where ClassId="4" order by adddate desc） D

//mysql版
Select * From （
select id,adddate,title,url from bArticle where ClassId="1" order by adddate desc limit 0,2） A
Union All
Select * From （
select id,adddate,title,url from bArticle where ClassId="2" order by adddate desc limit 0,2） B
Union All
Select * From （
select id,adddate,title,url from bArticle where ClassId="3" order by adddate desc limit 0,2） C
Union All
Select * From （
select id,adddate,title,url from bArticle where ClassId="4" order by adddate desc limit 0,2） D
http://blog.csdn.net/kemy88/archive/2007/02/28/1516913.aspx