如何将Linq转换为sql？

Question

I want write code for table, I know in SQL Server, but I don't know Linq or EF.

SQL Server code:

SELECT *
FROM Driver
WHERE id IN (SELECT Driver
             FROM Drive_Car
             WHERE Drive_Car.Finish_Date IS NOT NULL)

I wrote this code in EF but it does not match the SQL Server results:

var drivers = db.Drivers
                .Where(d => db.Drive_Car
                              .Where(dc => dc.Driver == d.ID && dc.Finish_Date != null)
                              .Select(dc => dc.Driver)
                              .Contains(d.ID));

Answer 1

This should be enough:

var drivers = db.Drivers
                .Where(d => db.Drive_Car
                              .Any(dc => dc.Driver == d.ID && dc.Finish_Date != null));

This leads to Exists , which is in the end about the same as the IN approach. Duplicating rows through join and uniquifing them back through distinct is not always optimized away and you may end up with more overhead than necessary, so I would not prefer that way.

Answer 2

You can get the same result using a Join operation. Or to split the command into 2 parts.

Linq SQL-Like syntax:

var query =
   (from d in db.Driver
   join dc in dc.Drive_Car on dc.Driver equals d.ID
   where dc.Finish_Date != null
   select d).Distinct();

Other method (Split into 2 parts)

var lst =
   (from dc in dc.Drive_Car 
   where dc.Finish_Date != null
   select dc.Driver).Distinct().ToList();

var query =
   (from d in db.Driver
    where lst.Contains(d.ID)
   select d);

References:

• Join/Where with LINQ and Lambda
• linq to sql Distinct and orderby