检查可能为 Null 的 Linq 查询

发布于 2024-11-05 08:36:15 字数 221 浏览 0 评论 0原文

为简单起见，我有 2 个表：

Table1 has UserId Email
Table2 has UserId Score

我想过滤掉所有分数 > 10. 但是，不能保证 Table2 中包含任何用户。 UserId是Table2上的PK和FK。 UserId 是表 1 上的 PK。

我的问题是我需要获取所有存在的分数，然后检查它们。

原文

I have for simplicity 2 tables:

Table1 has UserId Email
Table2 has UserId Score

I want to filter out all scores > 10. But, Table2 is not guaranteed to have any users in it. UserId is a PK and FK on Table2. UserId is a PK on table 1.

My issue is that I need to get all scores where they exist and then check them.

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行雁书 2024-11-12 08:36:16

请参阅左外连接

var q =

    from user in Table1 

    join s in Table2 on user.UserId  equals score.UserId  into lscore

    from score in lscore.DefaultIfEmpty()

    where score == null || lscore.score < 10

    select new { userId = user.userid,  email = user.Email, Score = score == null ? 0 : lscore.score };

See Left Outer Join

var q =

    from user in Table1 

    join s in Table2 on user.UserId  equals score.UserId  into lscore

    from score in lscore.DefaultIfEmpty()

    where score == null || lscore.score < 10

    select new { userId = user.userid,  email = user.Email, Score = score == null ? 0 : lscore.score };

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