sql语句查询结果合并union all用法_数据库技巧，需要的朋友可以参考下。
代码如下:
--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