如何排除不与另一个表连接的行? [英] How to exclude rows that don't join with another table?

问题描述

我有两张表，一张有主键，另一张是外键.

I have two tables, one has primary key other has it as a foreign key.

我想从主表中提取数据，只有当辅助表没有有包含它的键的条目时.与简单的内连接相反，它只返回通过该键连接在一起的行.

I want to pull data from the primary table, only if the secondary table does not have an entry containing it's key. Sort of an opposite of a simple inner join, which returns only rows that join together by that key.

推荐答案

SELECT <select_list> 
FROM Table_A A
LEFT JOIN Table_B B
ON A.Key = B.Key
WHERE B.Key IS NULL

加入的完整图像

来自文章:http://www.codeproject.com/KB/database/Visual_SQL_Joins.aspx

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