SQL Server 差异(与相交相反) [英] SQL Server Difference (opposite of intersect)

问题描述

寻找最简单/最具可扩展性的方式来做一组差异"；在 SQL Server 中，请参见下文.

Looking for the easist/most scalable way to do a set "difference" in SQL Server see below.

如果你不能从图片中看出我正在寻找所有不在十字路口的东西.

If you can't tell from the picture i am looking for everything that is not in the intersection.

我见过一种方法:

select * from (      
    (select 'test1' as a, 1 as b)
 union all
  (select 'test2' as a , 2 as b union all select 'test1' as a , 1 as b )
)un group by a,b  having count(1)=1

但我担心如果我使用两个大集合会发生什么(我不会从 select '' 常量语句中查询，我的查询将从真实表中提取.)

But i fear what would happen if i used two large sets (i will not be querying from select '' constant statements, my queries will be pulling from real tables.)

可能的解决方案...

drop table #temp_a;
drop table #temp_b;

 go


  select * into #temp_a from (
   select 1 as num, 'String' as two, 'int'as three, 'purple' as four union all
   select 2 as num, 'dog' as two, 'int'as three, 'purple' as four union all
   select 3 as num, 'dog' as two, 'int'as three, 'cat' as four ) a 

select * into #temp_b from (
  select 1 as num, 'String' as two, 'decimal'as three, 'purple' as four union all
  select 2 as num, 'dog' as two, 'int'as three, 'purple' as four union all
  select 3 as num, 'dog' as two, 'int'as three, 'dog' as four ) b 





   SELECT IsNull(a.num, b.num) A,IsNull(a.two, b.two) B, IsNull(a.three, b.three) C,                  
      IsNull(a.four, b.four) D 
     FROM #temp_a a 
   FULL OUTER JOIN #temp_b b ON (a.num=b.num AND a.two=b.two and a.three=b.three and a.four=b.four)
    WHERE   (a.num is null or b.num is null  )

结果:

1 String int Purple

1 String int purple

3 dog int cat

3 dog int cat

1 个字符串 dec 紫色

1 String dec purple

3 dog int dog

3 dog int dog

推荐答案

这样的事情怎么样?

SELECT A, B FROM Table1 EXCEPT SELECT A,B FROM Table2
UNION
SELECT A, B FROM Table2 EXCEPT SELECT A,B FROM Table1

这是一个使用 FULL OUTER JOIN 方法的例子(假设 A 在两个表中都不能为空)

Here is an example with the FULL OUTER JOIN method (assuming A is not nullable in both tables)

SELECT IsNull(Table1.A, Table2.A) a,IsNull(Table1.B, Table2.B) B
FROM Table1 
FULL OUTER JOIN Table2 ON (Table1.A=Table2.A AND Table1.B=Table2.B)
WHERE Table1.A is null or Table2.A is null

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