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--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)