如何选择未在另一个表中引用的列 [英] How do I select a column that I not referenced in another table

问题描述

-

SELECT DISTINCT p.region_no

AS noReference

FROM Provider p

WHERE NOT EXISTS（SELECT region_name FROM dbo.region

WHERE p.region_no = dbo.region.region_no）;



< b>我尝试过：



SELECT DISTINCT p.region_no

AS noReference

FROM Provider p

WHERE NOT EXISTS（SELECT region_name FROM dbo.region

WHERE p.region_no = dbo.region.region_no）

解决方案

尝试：

  SELECT   DISTINCT  p.Region_no  AS  noReference 
  FROM 提供者p 
 < span class =code-keyword> LEFT   JOIN 区域r  ON  p.Region_no = r.Region_no 
  WHERE  r.Region_no  IS   NULL  

SELECT DISTINCT region_no，region_name

FROM region r

WHERE r.region_no NOT IN（SELECT region_no

FROM provider） ;

-
SELECT DISTINCT p.region_no
AS noReference
FROM Provider p
WHERE NOT EXISTS (SELECT region_name FROM dbo.region
WHERE p.region_no = dbo.region.region_no );

What I have tried:

SELECT DISTINCT p.region_no
AS noReference
FROM Provider p
WHERE NOT EXISTS (SELECT region_name FROM dbo.region
WHERE p.region_no = dbo.region.region_no )

解决方案

Try:

SELECT DISTINCT p.Region_no AS noReference	
FROM Provider p 
LEFT JOIN Region r ON p.Region_no = r.Region_no
WHERE r.Region_no IS NULL

SELECT DISTINCT region_no, region_name
FROM region r
WHERE r.region_no NOT IN (SELECT region_no
FROM provider);

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