If you don’t know about the Hekaton engine of SQL Server 2014, please visit below an article.

SQL Server 2014: What is Hekaton?

I am very surprised with the feature list of SQL Server 2016 because it came with lots of features and improvements. Whenever I explored SQL Server 2016, I got something new.
SQL Server 2016 already enhanced In-Memory OLTP by introducing the list of features. Let me share one of the features here.

In the previous version, you cannot create a FOREIGN KEY in memory optimized table. Now, SQL Server 2016 introduced a feature to store the reference of a table in memory so you can create a FOREIGN KEY in memory optimized tables.

You can create a reference between memory optimized tables; you cannot give reference of a Non-memory optimized table to a memory optimized table.

Below is a full demonstration on this.

If you do not configure Memory optimized file group and data file, use below script to configure it.

Add Memory optimized file group:

ALTER DATABASE Database_Name
ADD Filegroup OLTP_InMemory CONTAINS MEMORY_OPTIMIZED_DATA

Add data file into created Memory optimized file group:

ALTER DATABASE Database_Name
ADD FILE (NAME = OLTP_InMemory, FILENAME = N'C:\SQLBackup\Hekaton')
TO FILEGROUP OLTP_InMemory

Create a sample In-Memory table:

CREATE TABLE tbl_Departments
(
	DeptID INT PRIMARY KEY NONCLUSTERED
	,DeptName VARCHAR(20)	
)WITH ( MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA)
GO

Create a another In-Memory child table:

CREATE TABLE tbl_Employee
(
	EmpID INT PRIMARY KEY NONCLUSTERED
	,EmpName VARCHAR(20)
	,DeptID INT
	,CONSTRAINT fk_tbl_Employee_EmpID FOREIGN KEY (DeptID) REFERENCES tbl_Departments(DeptID)
) WITH ( MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA);
GO

Try to give reference of Non-Memory optimized table to Memory optimized table:

CREATE TABLE tbl_EmpSalary
(
	EmpSalaryID INT PRIMARY KEY 
	,EmpID INT
	,EmpSalary INT
	,EmpSalaryMonth INT
	,CONSTRAINT fk_tbl_EmpSalary_EmpID FOREIGN KEY (EmpID) REFERENCES tbl_Employee(EmpID)
)
GO

You will get below errors:

Msg 10778, Level 16, State 0, Line 1
Foreign key relationships between memory optimized tables and non-memory optimized tables are not supported.
Msg 1750, Level 16, State 1, Line 1
Could not create constraint or index. See previous errors.

In this post, I am showing an Optimized Memory Table with allocating dedicated Memory Optimized File Group in SQL Server 2014.

In the Previous post, I discussed basic theory about In-Memory Engine of SQL Server 2014.

SQL Server 2014: What is Hekaton?

That is one of the optimized ways to the create an Optimized Memory Table in a dedicated File Group of SQL Server.

TSQL Script for creating the Memory Optimized File group and file:

USE [master]
GO
ALTER DATABASE [AdventureWorks_2014] 
  ADD FILEGROUP [Memory_Optimized] CONTAINS MEMORY_OPTIMIZED_DATA 
GO
ALTER DATABASE [AdventureWorks_2014] 
  ADD FILE ( NAME = N'Hekaton', FILENAME = N'C:\Program Files\Microsoft SQL Server\MSSQL11.MSSQLSERVER\MSSQL\DATA\Hekaton' ) 
   TO FILEGROUP [Memory_Optimized]
GO

Create a sample Memory Optimized Table:

USE AdventureWorks_2014
GO
CREATE TABLE dbo.tbl_Students
(
 StudentID int NOT NULL
 ,Name VARCHAR(50)
 ,Address VARCHAR
) WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA)
GO

Above table will create automatically into a Memory Optimized file group. We can access this table like any other table.