Linq 到 SQL - 使用 Where 子句按相关表排序

Question

I have two related tables lets say:

Table Products (Main Table)

• ID
• Name
• Type

Table Parts (Child of Products, contains detailled Information)

• ID
• ProductID
• PartName
• PartValue

I would like to get Products ordered by the value of a specific part (eG Engine)

I came up with the following:

// Code to construct a query to get all desired products
products = products.OrderBy(c => c.Parts.Where(d => d.PartName == "Engine").Select(d => d.Value).FirstOrDefault());

This works but is too slow. Can I improve the query or will I have to redsign my database so I won't be sorting like this in the first place?

Generated SQL-Query:

SELECT 
    [Project3].[ID] AS [ID], 
    [Project3].[Name] AS [Name]
    FROM ( SELECT 
        [Project2].[ID] AS [ID], 
        [Project2].[Name] AS [Name], 
        [Project2].[C1] AS [C1]
        FROM ( SELECT 
            [Extent1].[ID] AS [ID], 
            [Extent1].[Name] AS [Name], 
            (SELECT TOP (1) 
                [Extent2].[PartValue] AS [PartValue]
                FROM [dbo].[Parts] AS [Extent2]
                WHERE ([Extent1].[ID] = [Extent2].[ProductID]) AND (N'Engine' = [Extent2].[PartName])) AS [C1]
            FROM [dbo].[Products] AS [Extent1]
            WHERE (1 = [Extent1].[Type])
        )  AS [Project2]
    )  AS [Project3]
    ORDER BY [Project3].[C1] ASC

Answer 1

If you want to try a join, it would be a bit like this:

        Products
        .Join(Parts, pd => pd.ID, pt => pt.ProductID, (pd, pt) => new { pd.Name, pt.PartName, pt.PartValue })
        .Where(x => x.PartName == "Engine")
        .OrderBy(x => x.PartValue);

This would result in a single select statement without the inner selects from before