How to convert SQL query to LINQ lambda expression with inner join and subquery

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I want to convert following SQL query into LINQ lambda expression.

SQL

SELECT     Hod.* 
FROM       (
               SELECT * 
               FROM   tbLease_Approval 
               WHERE  UserRole = 'HOD' 
               AND    IsApproved = 1)
           ) AS Pm 
INNER JOIN (
               SELECT * 
               FROM   tbLease_Approval 
               WHERE  UserRole = 'Finance' 
               AND    IsApproved = 0
           ) AS Hod 
ON         Pm.LeaseNo = Hod.LeaseNo

What I have tried:

I tried to made query for inner join. But unable to create subquery part using LINQ lambda expression in following query.

C#

var test = db.Ett_LeaseApprovalDetails.Join(db.Ett_LeaseApprovalDetails,
                            r1 => r1.LeaseNo, r2 => r2.LeaseNo, (r1, r2) => 
                            new { r2.LeaseNo, r2.IsApproved, r2.IsRejected, r2.Remarks });

Posted 21-Sep-19 23:03pm

Pankaj sonar

Updated 23-Sep-19 4:45am

#realJSOP

v2

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#realJSOP · Answer 1 · 2019-09-22T02:05:00

This may not help you, but our team puts complex queries into a stored proc, and if necessary, uses Linq to filter out what we don't want in the app. That leaves the queries (that sql server is optimized to perform well) in the database, and is realizes significantly reduced Linq complexity and performance hit in the C# code. It also lets us deploy just database changes if the complex query needs to be adjusted.

Finally, your query seems overly complex. Wouldn't this do the job as well:

SQL

SELECT * 
FROM   tbLease_Approval 
WHERE  (UserRole = 'HOD'     AND IsApproved = 1)
OR     (UserRole = 'Finance' AND IsApproved = 0)

Richard Deeming · Answer 2 · 2019-09-23T04:46:00

A quick rewrite of your SQL query might make things easier:

SQL

SELECT
    *
FROM
    tbLease_Approval As Hod
WHERE
    Hod.UserRole = 'Finance'
And
    Hod.IsApproved = 0
And
    Exists
    (
        SELECT 1
        FROM tbLease_Approval As Pm
        WHERE Pm.UserRole = 'HOD'
        And Pm.IsApproved = 1
        And Pm.LeaseNo = Hod.LeaseNo
    )
;

That should translate nicely to LINQ:

C#

var test = from hod in db.Ett_LeaseApprovalDetails
           where hod.UserRole = "Finance"
           && !hod.IsApproved
           && db.Ett_LeaseApprovalDetails.Any(pm => pm.UserRole = "HOD" && pm.IsApproved && pm.LeaseNo == hod.LeaseNo)
           select hod;

How to convert SQL query to LINQ lambda expression with inner join and subquery

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