---
title: "How to use SQL Join in LINQ?"  
description: "How to use SQL Join in LINQ?"  
author: "Ethan Karla"  
published: 2021-09-24  
updated: 2021-09-24  
canonical: https://www.mindstick.com/forum/156767/how-to-use-sql-join-in-linq  
category: "linq"  
tags: ["c#", "ado.net", "linq"]  
reading_time: 9 minutes  

---

# How to use SQL Join in LINQ?

How to use SQL [Join in LINQ](https://www.mindstick.com/forum/33665/how-to-use-join-in-linq-query-mvc) like [INNER JOIN](https://www.mindstick.com/forum/33572/sql-inner-join-keyword), [LEFT OUTER JOIN](https://www.mindstick.com/articles/12231/types-of-join-in-sql-server), [CROSS JOIN](https://www.mindstick.com/interview/1850/what-is-cross-join), and [GROUP](https://yourviews.mindstick.com/view/81323/adani-green-energy-group-bags-world-s-biggest-solar-bid) JOIN [explain](https://www.mindstick.com/forum/157854/what-is-system-debugging-explain-some-system-debugging-tools-used-in-modern-computer-systems) with example?

## Replies

### Reply by Ravi Vishwakarma

## Join in LINQ

In LINQ, join operators are used to join more than one list or the collection and get the matched data from the collection based on condition. The LINQ join operator functionality are the same as the [SQL Join](https://www.mindstick.com/forum/159370/sql-join-returns-null-records-when-there-is-no-data-in-the-database-in-sql-server-why) query.

## LINQ has different types of joins

1. Inner Join - it returns the elements from the collection which satisfy the condition
2. Left [Outer Join](https://www.mindstick.com/forum/159328/mysql-outer-join-syntax-error) - it return the all element from the left side collection and matched collection from right side collection
3. [Cross](https://www.mindstick.com/forum/33892/how-to-handle-cross-thread-exception-in-winforms) Join - it returns some product of elements from the collection
4. Group Join -

## Inner Join Example -

```
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
 public static void Main()
 {
  List<Subject> subjects = new List<Subject>(){
   new Subject() { SubjectId = 1, SubjectName = 'C#'},
   new Subject() { SubjectId = 2, SubjectName = 'C++'},
   new Subject() { SubjectId = 3, SubjectName = 'C'},
   new Subject() { SubjectId = 4, SubjectName = 'Python'},
   new Subject() { SubjectId = 5, SubjectName = 'Java'}
  };
  List<Student> students = new List<Student>(){
  new Student() { StudentId = 1, Name = 'Ashu', Marks = 500,SubjectId=2 },
  new Student() { StudentId = 2, Name = 'Shyam', Marks = 500,SubjectId=3},
  new Student() { StudentId = 3, Name = 'Shriyam', Marks = 400,SubjectId=2 },
  new Student() { StudentId = 4, Name = 'Sunny', Marks = 550,SubjectId=4 },
  new Student() { StudentId = 5, Name = 'Ram', Marks = 600,SubjectId=3 },
  new Student() { StudentId = 6, Name = 'Krishna', Marks = 550,SubjectId=2 },
  new Student() { StudentId = 7, Name = 'Anupam', Marks = 550,SubjectId=5 }
  } ;
  // inner join command
  var result = from student in students
  join subject in subjects
  on student.SubjectId equals subject.SubjectId
  select new
  {
  StudentName = student.Name,
  SubjectName = subject.SubjectName,
  ID = student.StudentId
  };
  Console.WriteLine('Inner Join\n');
  Console.WriteLine('{0,3} {1,-15}  {2,-10}','ID', 'StudentName', 'Subject');
  foreach(var item in result)
   Console.WriteLine('{0,3} {1,-15} {2,-10}',item.ID, item.StudentName,item.SubjectName);
  //
  Console.ReadLine();
 }
}
```

```
class Student
{
public int StudentId { get; set; }
public string Name { get; set; }
public int Marks { get; set; }
public int SubjectId { get; set; }
}
```

```
class Subject{
 public int SubjectId { get; set; }
 public string SubjectName { get; set; }
}
```

## Output

```
Inner Join
 ID StudentName     Subject
  1 Ashu            C++
  2 Shyam           C
  3 Shriyam         C++
  4 Sunny           Python
  5 Ram             C
  6 Krishna         C++
  7 Anupam          Java
```

## Left Outer Example -

```
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
 public static void Main()
 {
  List<Subject> subjects = new List<Subject>(){
   new Subject() { SubjectId = 1, SubjectName = 'C#'},
   new Subject() { SubjectId = 2, SubjectName = 'C++'},
   new Subject() { SubjectId = 3, SubjectName = 'C'},
   new Subject() { SubjectId = 4, SubjectName = 'Python'},
   new Subject() { SubjectId = 5, SubjectName = 'Java'}
  };
  List<Student> students = new List<Student>(){
  new Student() { StudentId = 1, Name = 'Ashu', Marks = 500,SubjectId=2 },
  new Student() { StudentId = 2, Name = 'Shyam', Marks = 500,SubjectId=3},
  new Student() { StudentId = 3, Name = 'Shriyam', Marks = 400 },
  new Student() { StudentId = 4, Name = 'Sunny', Marks = 550,SubjectId=4 },
  new Student() { StudentId = 5, Name = 'Ram', Marks = 600,SubjectId=3 },
  new Student() { StudentId = 6, Name = 'Krishna', Marks = 550,SubjectId=5 },
  new Student() { StudentId = 7, Name = 'Anupam', Marks = 550 }
  } ;
  // left outer join command
  var result = from student in students
  join subject in subjects
  on student.SubjectId equals subject.SubjectId into stusub
  from ss in stusub.DefaultIfEmpty()
  select new
  {
  StudentName = student.Name,
  SubjectName =  ss == null ? 'No Subject Choose' : ss.SubjectName,
  ID = student.StudentId
  };
  Console.WriteLine('Left outer Join\n');
  Console.WriteLine('{0,3} {1,-15}  {2,-10}','ID', 'StudentName', 'Subject');
  foreach(var item in result)
   Console.WriteLine('{0,3} {1,-15} {2,-10}',item.ID, item.StudentName,item.SubjectName);
  //
  Console.ReadLine();
 }
}
```

```
class Student
{
public int StudentId { get; set; }
public string Name { get; set; }
public int Marks { get; set; }
public int SubjectId { get; set; }
}
```

```
class Subject{
 public int SubjectId { get; set; }
 public string SubjectName { get; set; }
}
```

## Output

```
Left outer Join
 ID StudentName      Subject
  1 Ashu            C++
  2 Shyam           C
  3 Shriyam         No Subject Choose
  4 Sunny           Python
  5 Ram             C
  6 Krishna         Java
  7 Anupam          No Subject Choose
```

## Cross Join LINQ

```
using System;
using System.Collections.Generic;
using System.Linq;
public class Program
{
 public static void Main()
 {
  List<Subject> subjects = new List<Subject>(){
   new Subject() { SubjectId = 1, SubjectName = 'C#'},
   new Subject() { SubjectId = 2, SubjectName = 'C++'},
   new Subject() { SubjectId = 3, SubjectName = 'C'},
   new Subject() { SubjectId = 4, SubjectName = 'Python'},
   new Subject() { SubjectId = 5, SubjectName = 'Java'}
  };
  List<Student> students = new List<Student>(){
  new Student() { StudentId = 1, Name = 'Ashu', Marks = 500,SubjectId=2 },
  new Student() { StudentId = 2, Name = 'Shyam', Marks = 500,SubjectId=3},
  new Student() { StudentId = 3, Name = 'Shriyam', Marks = 400 },
  new Student() { StudentId = 4, Name = 'Sunny', Marks = 550,SubjectId=4 },
  new Student() { StudentId = 5, Name = 'Ram', Marks = 600,SubjectId=3 },
  new Student() { StudentId = 6, Name = 'Krishna', Marks = 550,SubjectId=5 },
  new Student() { StudentId = 7, Name = 'Anupam', Marks = 550 }
  } ;
  // left outer join command
  var result = from student in students
      from subject in subjects
  select new
  {
  StudentName = student.Name,
  SubjectName =  subject.SubjectName,
  ID = student.StudentId
  };
  Console.WriteLine('Cross Join\n');
  Console.WriteLine('{0,3} {1,-15}  {2,-10}','ID', 'StudentName', 'Subject');
  foreach(var item in result)
   Console.WriteLine('{0,3} {1,-15} {2,-10}',item.ID, item.StudentName,item.SubjectName);
  //
  Console.ReadLine();
 }
}
class Student
{
public int StudentId { get; set; }
public string Name { get; set; }
public int Marks { get; set; }
public int SubjectId { get; set; }
}
class Subject{
 public int SubjectId { get; set; }
 public string SubjectName { get; set; }
}
```

## Example

```
Cross Join
 ID StudentName      Subject
  1 Ashu            C#
  1 Ashu            C++
  1 Ashu            C
  1 Ashu            Python
  1 Ashu            Java
  2 Shyam           C#
  2 Shyam           C++
  2 Shyam           C
  2 Shyam           Python
  2 Shyam           Java
  3 Shriyam         C#
  3 Shriyam         C++
  3 Shriyam         C
  3 Shriyam         Python
  3 Shriyam         Java
  4 Sunny           C#
  4 Sunny           C++
  4 Sunny           C
  4 Sunny           Python
  4 Sunny           Java
  5 Ram             C#
  5 Ram             C++
  5 Ram             C
  5 Ram             Python
  5 Ram             Java
  6 Krishna         C#
  6 Krishna         C++
  6 Krishna         C
  6 Krishna         Python
  6 Krishna         Java
  7 Anupam          C#
  7 Anupam          C++
  7 Anupam          C
  7 Anupam          Python
  7 Anupam          Java    
```

## Cross Join LINQ

```
using System;using System.Collections.Generic;using System.Linq;
public class Program{ public static void Main() {  List<Subject> subjects = new List<Subject>(){   new Subject() { SubjectId = 1, SubjectName = 'C#'},   new Subject() { SubjectId = 2, SubjectName = 'C++'},   new Subject() { SubjectId = 3, SubjectName = 'C'},   new Subject() { SubjectId = 4, SubjectName = 'Python'},   new Subject() { SubjectId = 5, SubjectName = 'Java'}  };
  List<Student> students = new List<Student>(){  new Student() { StudentId = 1, Name = 'Ashu', Marks = 500,SubjectId=2 },  new Student() { StudentId = 2, Name = 'Shyam', Marks = 500,SubjectId=3},  new Student() { StudentId = 3, Name = 'Shriyam', Marks = 400 },  new Student() { StudentId = 4, Name = 'Sunny', Marks = 550,SubjectId=4 },  new Student() { StudentId = 5, Name = 'Ram', Marks = 600,SubjectId=3 },  new Student() { StudentId = 6, Name = 'Krishna', Marks = 550,SubjectId=5 },  new Student() { StudentId = 7, Name = 'Anupam', Marks = 550 }  } ;
  // left outer join command
  var result = from subject in subjects              join student in students               on  subject.SubjectId equals student.SubjectId into stusub  select new  {  SubjectName =  subject.SubjectName,   Student = from stu in stusub   orderby stu.Name   select stu  };
  Console.WriteLine('Group Join\n');  foreach(var item in result)  {   Console.WriteLine(item.SubjectName + ' Subject \n');   if(item.Student.ToList().Count() == 0)    Console.WriteLine('\tNo availible student\n');   else   {   item.Student.ToList().ForEach( stu => Console.WriteLine('\t' + stu.StudentId + ' | ' + stu.Name ));    Console.WriteLine();   }  }  Console.ReadLine(); }}
class Student{public int StudentId { get; set; }public string Name { get; set; }public int Marks { get; set; }public int SubjectId { get; set; }
}
class Subject{ public int SubjectId { get; set; } public string SubjectName { get; set; }}
```

## Output

```
Group Join
C# Subject
    No availible student
C++ Subject
    1 | Ashu
C Subject
    5 | Ram    2 | Shyam
Python Subject
    4 | Sunny
Java Subject
    6 | Krishna
```

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---

Original Source: https://www.mindstick.com/forum/156767/how-to-use-sql-join-in-linq

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