如何检查表格的一列中的条目是否在另一列中至少出现一次？

Question

我有一张表格，看起来像这样？

CREATE TABLE [dbo].[WordForm] (
    [Word1] VARCHAR (20) NOT NULL, 
    [Word2] VARCHAR (20) NOT NULL 
} 

这是数据的样子吗？

Word1  Word2 
-----  ----- 
abandon  abandon 
abandon  abandonment 
adapt  adapt 
adapt  adaptable 
adapt  adaptation 
adapt  adapter 
adversely adverse 
adversely adversely 
adversely adversity 

如何检查每一个出现在列字1字存在于字2至少一次，并且如果有出现WORD1中而不是字2我需要知道的话是什么话。

Answer 1

有关大型数据集更高性能的解决方案试试这个：

SELECT w.Word1 as [Word 1 Not in Word 2] 
FROM WordForm w 
EXCEPT 
SELECT w.Word2 
FROM WordForm w 
; 

SELECT w.Word2 as [Word 2 Not in Word 1] 
FROM WordForm w 
EXCEPT 
SELECT w.Word1 
FROM WordForm w 
; 

Answer 2

SELECT w.Word1 as [Word 1 Not in Word 2] 
FROM WordForm w 
WHERE NOT EXISTS 
     (
      SELECT * 
      FROM WordForm x 
      WHERE x.Word2 = w.Word1 
     ) 

SELECT w.Word2 as [Word 2 Not in Word 1] 
FROM WordForm w 
WHERE NOT EXISTS 
     (
      SELECT * 
      FROM WordForm x 
      WHERE x.Word1 = w.Word2 
     ) 

Answer 3

有2个本地运营商对于这一点，INTERSECT和EXCEPT：

select word1 from wordform 
intersect 
select word2 from wordform 

select word1 from wordform 
except 
select word2 from wordform 

https://msdn.microsoft.com/en-us/library/ms188055.aspx