需要从两个表列中选择不重复的值 [英] Need to select the non-duplicate values from two table columns

问题描述

我有两张带有城市名称的表格.我想根据第二个表检查第一个表，如果第一个表在第二个表中不包含城市名称，则选择它进行显示.因此，如果城市在两个表中，则不要显示它.

I have two tables with city names in them. I want to check the first table against the second table and if the first table does not contain a city name in the second table then select it to display. So if the city is in both tables, then do not display it.

我知道我可以这样做来找到匹配的:

I know that I can do this to find the ones that match:

WHERE table1.city=table2.city

但是当我尝试将其用于不匹配的事物时:

But when I try to use this for things that dont match:

Where table1.city!=table2.city

我仍然得到匹配的城市.

I still get the cities that match.

推荐答案

SELECT `city_name` 
FROM `first_table`
WHERE `city_name` NOT IN (SELECT `city_name` FROM `second_table`)

将从第一个表中选择不在第二个表中的城市名称.

Will select city names from the first table that are not in second table.

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