如何使用LINQ实现左排除JOIN? [英] How to achieve Left Excluding JOIN using LINQ?

问题描述

如何使用LINQ实现左排除JOIN?

How to achieve Left Excluding JOIN using LINQ?

在 SQL 中:

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

推荐答案

您需要DefaultIfEmpty()作为LEFT JOIN，然后您可以检查所连接的值是否为null:

You need DefaultIfEmpty() for the LEFT JOIN, then you can check if the joined value is null:

var result = from a in Table_A
             join b in Table_B on a.Key equals b.Key into j
             from b in j.DefaultIfEmpty()
             where b == null
             select new { ... };

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