如何获取仅包含列2的给定值的列1的值？ [英] How to fetch values of column 1 that contain only the given value of column 2?

问题描述

我想选择仅出现在墨西哥而不是其他任何国家的名字。

I want to select names that only appear in Mexico and not in any other country.

Country      |  Name      
-------------|------------
Mexico       |  Vallejo
Mexico       |  Rachel
United States|  Rachel
UK           |  Rachel
Australia    |  Rachel
Mexico       |  Amy
Canada       |  Amy 
Mexico       |  Annette
Mexico       |  Jennifer
Swahili      |  Jennifer 
Mexico       |  Benedict 

正确的查询将仅返回以下名称。

The correct query would only return the following names.

Name      
---------
Annette
Benedict
Vallejo

有什么想法吗？我不确定这是否是DISTINCT和WHERE条件的混合。

Any ideas? I'm not sure if this might be a mix of DISTINCT and WHERE conditions.

推荐答案

我认为您想要类似的东西

I think you want something like

SELECT Name
FROM <table>
WHERE Country = 'Mexico'
AND Name NOT IN (
    SELECT Name
    FROM <table>
    WHERE Country <> 'Mexico')

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