SQL:EXCEPT 查询

Question

这是我试图实现的基本示例:

create table #testing (
     tab varchar(max), a int, b int, c int )

insert into #testing VALUES ('x',1, 2, 3)
insert into #testing VALUES ('y',1, 2, 3)  
insert into #testing VALUES ('x', 4, 5, 6)  

select * from #testing

这将产生表:

 tab     a    b    c
-----------------------
  x      1    2    3
  y      1    2    3
  x      4    5    6

然后我想根据 a、b、c 的值比较“tab”上的行:

select a,b,c from #testing where tab = 'x'
except
select a,b,c from #testing where tab= 'y'

这给了我我期待的答案:

a    b    c
------------
4    5    6

但是我还想在我的结果集中包含 Tab 列，所以我想要这样的东西:

 Select tab,a,b,c from #testing where ????
            (select a,b,c from #testing where tab = 'x'
             except
             select a,b,c from #testing where tab= 'y')

我将如何实现这一目标？

Answer 1

使用 not exists :

select a.*
from #testing a
where a.tab = 'x' 
      and not exists (
                       select * 
                       from #testing t 
                       where t.a = a.a and t.b = a.b and t.c = a.c and t.tab = 'y'
                     )

在这里你可以获得 SQL Fiddle 演示:DEMO