哇，union的优先级很高嘛

72 阅读 0 评论 48 点赞

我是靠谱客的博主简单彩虹，这篇文章主要介绍哇，union的优先级很高嘛，现在分享给大家，希望可以做个参考。

原来，union的优先级很高。比如

复制代码

1
2
3
4
5
6
7
8
select stdname,[subject]='化学',化学 as score  from #student2 
union all 
select stdname,[subject]='数学',数学 as score  from #student2 
union all 
select stdname,[subject]='物理',物理 as score  from #student2 
union all 
select stdname,[subject]='语文',语文 as score  from #student2 
order by stdname,[subject]

等同于

复制代码

1
2
3
4
5
6
7
8
9
10
select * from(
select stdname,[subject]='化学',化学 as score  from #student2 
union all 
select stdname,[subject]='数学',数学 as score  from #student2 
union all 
select stdname,[subject]='物理',物理 as score  from #student2 
union all 
select stdname,[subject]='语文',语文 as score  from #student2 
) as a
order by stdname,[subject]