LINQ实体框架中的WITH语句

Question

I got a SQL code like this which I'm going to use in a .NET application, I'm familiar with LINQ but I don't know what to do with the WITH statement.

WITH records
AS
(
    SELECT  [key], [rev], [IsCurrent],
            ROW_NUMBER() OVER(PARTITION BY [key]
            ORDER BY CASE WHEN [rev] = @revNUm          
            THEN 0 ELSE 1 END) rn
    FROM    tableName
    WHERE   [Rev] IN (@revNUm,0)
)
SELECT  [key], [rev], [IsCurrent]
FROM    records 
WHERE   rn = 1

EDIT: The ROW_NUMBER() seems to be hard aswell, how do I do that?

Thanks

Answer 1

It looks like you're taking the first record in each key grouping where rev is 0 or equals the revnum parameter. You can do that in Linq with:

 var query = db.records
               .OrderBy(r => r.rev == revNum ? 0 : 1)
               .Where(r => rev == 0 || rev == revNum)
               .GroupBy(r => r.key)
               .Select(g => g.First());

if records contains more that the three fields in the query then just add

               .Select(r => new {r.key, r.rev, r.IsCurrent})

Answer 2

Save the query as a stored procedure and using LINQ, call the stored procedure (see here: http://msdn.microsoft.com/en-us/library/bb918119.aspx ). Something like this:

CREATE PROCEDURE newprocedure
@revNUm INT
AS    
BEGIN
WITH records
AS
(
    SELECT  [key], [rev], [IsCurrent],
            ROW_NUMBER() OVER(PARTITION BY [key]
            ORDER BY CASE WHEN [rev] = @revNUm          
            THEN 0 ELSE 1 END) rn
    FROM    tableName
    WHERE   [Rev] IN (@revNUm,0)
)
SELECT  [key], [rev], [IsCurrent]
FROM    records 
WHERE   rn = 1
END

Answer 3

Create Inline table valued function from your code

CREATE FUNCTION YourFunction
(   
)
RETURNS TABLE 
AS
RETURN 
(
WITH records
AS
(
    SELECT  [key], [rev], [IsCurrent],
            ROW_NUMBER() OVER(PARTITION BY [key]
            ORDER BY CASE WHEN [rev] = @revNUm          
            THEN 0 ELSE 1 END) rn
    FROM    tableName
    WHERE   [Rev] IN (@revNUm,0)
)
SELECT  [key], [rev], [IsCurrent]
FROM    records 
WHERE   rn = 1
)
GO

Drop this function to your DBML designer. This way you'll get the fastest execution time and easiest way of implementation.