比较两个SQL表并返回缺少的ID? [英] Compare two SQL tables and return missing ids?

问题描述

我有两个简单的表:(这里只有"id"列)

I have two simple tables: (here only the "id" column)

表1:

id
1
2
3
4

表2:

id
2
4

sql查询应该比较两个表中table2中缺少的"id"并返回: 1,2

the sql query should compare the two tables for missing "id" in table2 and return: 1,2

有什么想法吗? :) TY

any ideas? :) TY

推荐答案

有几种方法可以给这只猫换皮:

There are several ways to skin this cat:

SELECT    table1.ID
FROM      table1
WHERE     table1.ID NOT IN(SELECT table2.ID FROM table2)

或者您可以使用左外部联接:

Or you could use a left outer join:

SELECT          table1.ID
FROM            table1
LEFT OUTER JOIN table2 ON table1.ID = table2.ID
WHERE           table2.ID IS NULL

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