Question

我正在尝试为我的上下文创建一个“AssociateWith”数据加载选项，以过滤当前用户有权访问的行。我的简单数据模型是这样的：

表格
UserPermissions
PK：ID
FK：RelatedUserID可以为空的 FK：RelatedItemID不可为空

用户
PK：ID

产品
PK：ID
FK：RelatedCategoryID不可为空

分类 PK：ID

在我的datacontext上，我正在尝试做类似的事情：

//dbContext is my LINQ context 
//current_user_id is the id of my current logged in user 
var dlo = new DataLoadOptions();
//issue->UsersPermissions is one->many relationship
// if I omit this LoadWith line, no associatewith filter
// is created in the generated sql code
dlo.LoadWith<Items>(i=>i.UserPermissions); 

dlo.AssociateWith<Items>(i=>
i.UserPermissions.Where(p=>
p.RelatedUserID.HasValue && p.RelatedUserID.Value == current_users_id));
dbContext.LoadOptions = dlo;

对我来说，一切似乎都是合理的，但在SQL中生成的查询如下所示：

SELECT [t0].[ID], [t1].[ID] AS [ID2], [t1].[RelatedUserID], [t1].[RelatedItemID] 
(SELECT COUNT(*)
FROM [dbo].[UserPermissions] AS [t2]
WHERE (([t2].[RelatedUserID] = @p0)) AND ([t2].[RelatedItemID] = [t0].[ID])
) AS [value]
FROM [dbo].[Items] AS [t0]
LEFT OUTER JOIN [dbo].[UserPermissions] AS [t1] ON ([t1].[RelatedUserID] = @p0) 
AND     
([t1].[RelatedItemID] = [t0].[ID])
ORDER BY [t0].[ID], [t1].[ID]

如何强制INNER JOIN而不是LEFT OUTER JOIN？我是否在后端错误地模拟了我的关系？

感谢您的帮助。

MMAS

Answer 1

LINQ to SQL生成LEFT OUTER JOIN只是因为UserPermissions.RelatedUserID列可以为空。底层的LINQ提供程序不够“智能”，无法进一步优化该查询到简单的INNER JOIN。我认为你无法做到这一点。

LINQ AssociateWith用于生成LEFT JOIN而不是INNER JOIN的数据上下文

1 个答案: