LINQ implements various connections to T-SQL

In the ORM framework of the big line of the today, for the. NET industry people, want to learn EF, that LINQ learning is imperative AH. Today summarizes the common use of table connections.

Inner Join

Linq:

1   var list = ( from in customerdb.order2in                               Customerdb.orderitem on C.orderid equals O.orderitemid3                             Selectnew {c = c. OrderId}). FirstOrDefault ();

The generated SQL

1 SELECT TOP(1) 2 [Extent1].[OrderId]  as [OrderId]3  from  [dbo].[Orders]  as [Extent1]4 INNER JOIN [dbo].[OrderItems]  as [Extent2]  on [Extent1].[OrderId] = [Extent2].[Orderitemid]

Left Join

      LINQ:

 1  var  list = (from  c in   Customerdb.order  2  join o in   custome Rdb.orderitem on C.orderid equals o.orderitemid  3   into GRP  4  from  grp in   Grp.defaultifempty ()  5  select  
   
    new  {c = c.orderid, GRP = grp. Orderitemid}). FirstOrDefault (); 
   

Generated sql:

1 SELECT TOP(1) 2 [Extent1].[OrderId]  as [OrderId], 3 [Extent2].[Orderitemid]  as [Orderitemid]4  from  [dbo].[Orders]  as [Extent1]5  Left OUTER JOIN [dbo].[OrderItems]  as [Extent2]  on [Extent1].[OrderId] = [Extent2].[Orderitemid]

Cross Join

Linq:

1     var list = ( from in customerdb.order2                               3                             Selectnew {c = c.orderid,o=o.orderitemid}). FirstOrDefault ();

Generated sql:

1 SELECT TOP (123[extent2].[ Orderitemid] as [Orderitemid]4from  [dbo].[ Orders] as [Extent1]5 cross JOIN [dbo]. [OrderItems] As [Extent2]

Summary: The right connection is actually the order position of the two tables replaced,

The whole connection is to put the results of the left outer join together to go heavy on the line.

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LINQ implements various connections to T-SQL