Microsoft SQL Server 2016 comes with a variety of new additions and I am happy for exploring the new features of SQL Server 2016.

Microsoft SQL Server 2014 introduced Hekaton engine which used for In-Memory Database objects.

SQL Server 2014: Create Memory Optimized File Group and Table

SQL Server 2016 introduced Columnstore index for Memory-Optimized Table which was not possible previously.
If you are planning to store large amount of data In Memory, you can apply Columnstore Index on that In Memory OLTP Table.

It comes with one condition: you can not apply Columnstore Index on the particular column. It must apply to all the columns of In-Memory Table.

Small demonstration with all the possible errors:

Create a sample memory optimized table with column store index:

CREATE TABLE tbl_Employees
(
	EmpID INT
	,EmpName VARCHAR(50)
	,EmpSalary INT
	,EmpDOJ DATETIME
	,INDEX idx_tbl_Employees_columnstore CLUSTERED COLUMNSTORE 
)
WITH (MEMORY_OPTIMIZED = ON)
GO

You will get a below error:

Msg 41321, Level 16, State 7, Line 1
The memory optimized table 'tbl_Employees' with DURABILITY=SCHEMA_AND_DATA must have a primary key.

Add primary key on script and execute it:

CREATE TABLE tbl_Employees
(
	EmpID INT PRIMARY KEY
	,EmpName VARCHAR(50)
	,EmpSalary INT
	,EmpDOJ DATETIME
	,INDEX idx_tbl_Employees_columnstore CLUSTERED COLUMNSTORE 
)
WITH (MEMORY_OPTIMIZED = ON)
GO

You will get a below error:

Msg 12317, Level 16, State 78, Line 3
Clustered indexes, which are the default for primary keys, are not supported with memory optimized tables. Specify a NONCLUSTERED index instead.

Apply Non Clustered Primary key and execute it:

CREATE TABLE tbl_Employees
(
	EmpID INT PRIMARY KEY NONCLUSTERED
	,EmpName VARCHAR(50)
	,EmpSalary INT
	,EmpDOJ DATETIME
	,INDEX idx_tbl_Employees_columnstore CLUSTERED COLUMNSTORE 
)
WITH (MEMORY_OPTIMIZED = ON)
GO

If you have not created Memory Optimized File group and related files, you may get a below error:

Msg 41337, Level 16, State 100, Line 1
Cannot create memory optimized tables. To create memory optimized tables, the database must have a MEMORY_OPTIMIZED_FILEGROUP that is online and has at least one container.

Create memory optimized file group and data files:

USE [master]
GO
ALTER DATABASE [Database_Name] 
ADD FILEGROUP [Memory_Optimized] CONTAINS MEMORY_OPTIMIZED_DATA 
GO
ALTER DATABASE [Database_Name] 
ADD FILE ( NAME = N'HekatonMemory', FILENAME = N'C:\Hekaton\hek.mdf' ) 
TO FILEGROUP [Memory_Optimized]
GO

SQL Server 2014 introduced the concept of In-Memory Database which provides the best combination of RDBMS + In-Memory Database.

SQL DBA is monitoring the size of tables, indexes and other fragmentation related information.

When we say that SQL Server tables stored in memory, we should also keep our eyes open on the utilization of memory.

SQL Server 2014 also introduced one DMV (sys.dm_db_xtp_table_memory_stats) to check the memory utilization of Memory Optimized Tables.
Using this view, you can find memory information like allocated memory and used memory for tables and indexes.

Executed below query on AdventureWorks2016ctp3:

SELECT  
	OBJECT_ID 
	,OBJECT_SCHEMA_NAME(object_id) + '.' + OBJECT_NAME(object_id) AS TableName
	,memory_allocated_for_table_kb 
	,memory_used_by_table_kb 
	,memory_allocated_for_indexes_kb 
	,memory_used_by_indexes_kb
FROM sys.dm_db_xtp_table_memory_stats
GO

Please visit other related articles:

SQL Server 2014: What is Hekaton?

SQL Server 2014: Create Memory Optimized File Group and Table

SQL Server: Find the total row count and size of the Tables

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.

What is In-memory Database?

Database Theory: What is In-memory Database?

What is Hekaton in SQL Server 2014?

SQL Server 2014: What is Hekaton?

How to create memory optimized table in SQL Server 2014?

SQL Server 2014: Create Memory Optimized File Group and Table

I want to turn the unique record from multiple rows to multiple column values. Is it possible in SQL Server?

Yes, We can do this task using PIVOT.

SQL Server has a PIVOT relational operator to turn the unique values of a specified column from multiple rows into multiple column values in the output (cross-tab), effectively rotating a table. It also allows performing aggregations, wherever required, for column values that are expected in the final output. The basic syntax for a PIVOT relational operator looks like this:

SELECT [ColumnNames] FROM [TableName]
PIVOT
(
AggregateFunction([ColumnToBeAggregated])
FOR PivotColumn IN ([PivotColumnValues])
) AS Alias

Do you know about the UNPIVOT?

UNPIVOT is another relational operator in SQL Server that performs almost the reverse operation of PIVOT, by rotating column values into rows values.

Using UNPIVOT, Do you think that you can get all correct value which are pivoted using PIVOT?

If you refer back, I said UNPIVOT is almost the reverse of the PIVOT operator; this means it might or might not be exactly the same. The reason is, Pivot performs aggregation while rotating row values into column values and might merge possible multiple row values into single column value in the output.

What is the WITH CHECK OPTION clause for a view?

The WITH CHECK OPTION for a view prevents data modifications (to the data) that do not confirm to the WHERE clause of the view definition. This allows data to be updated via the view, but only if it belongs in the view.

How you are checking that record is exists in database or not?

Using EXISTS clause:

IF EXISTS(SELECT 1 FROM dbo.Customer WITH(NOLOCK) WHERE CustId = @CustId)
    BEGIN
        PRINT 'Record Exists'
    END
ELSE
    BEGIN
        PRINT 'Record doesn''t Exists'
    END
END IF;

What is the meaning of the WITH SCHEMABINDING clause?

• SCHEMABINDING binds the view to the schema of the underlying table or tables. When SCHEMABINDING is specified, the base table or tables cannot be modified in a way that would affect the view definition.
• The view definition itself must first be modified or dropped to remove dependencies on the table that is to be modified.
• All referenced objects must be in the same database. Views or tables that participate in a view created with the SCHEMABINDING clause cannot be dropped unless that view is dropped or changed so that it no longer has schema binding. Otherwise, the Database Engine raises an error.
• Also, executing ALTER TABLE statements on tables that participate in views that have schema binding fail when these statements affect the view definition.
• The implementation of SCHEMABINDING would increase stability and performance of the system, but also increase the amount of developers’ work.

Can we use WITH SCHEMABINDING in Stored Procedures?

No: We cannot use WITH SCHEMABINDING in stored procedures.

What are the main disadvantages of the WITH SCHEMABINDING clause?

It would take more time to make changes in tables’ structure. If I just want to change the size of one column, I will need to modify before and after several views.

The automated test of the application can catch all broken views and functions. This will not increase the amount of developers’ work.

You can not change the collation of a database with schemabound objects.

What do you know about the OFFSET FETCH clause of the SQL Server 2012?

The OFFSET-FETCH clause provides you with an option to fetch only a window or page of results from the result set. OFFSET-FETCH can be used only with the ORDER BY clause.

OFFSET: Specifies the number of rows to skip, before starting to return rows from the query expression. The argument for the OFFSET clause can be an integer or expression that is greater than or equal to zero. You can use ROW and ROWS interchangeably.

FETCH: Specifies the number of rows to return, after processing the OFFSET clause. The argument for the FETCH clause can be an integer or expression that is greater than or equal to one. You can use ROW and ROWS interchangeably. Similarly, FIRST and NEXT can be used interchangeably.

Please write a script or logic of custom paging using OFFSET and FETCH NEXT.

SQL Server 2012: Custom paging using OFFSET and FETCH NEXT

What are the limitations of OFFSET and FETCH clause of the SQL Server 2012?

• ORDER BY is mandatory to use OFFSET and FETCH clause.
• OFFSET clause is mandatory with FETCH. You can never use, ORDER BY … FETCH.
• TOP cannot be combined with OFFSET and FETCH in the same query expression.
• The OFFSET/FETCH rowcount expression can be any arithmetic, constant, or parameter expression that will return an integer value. The rowcount expression does not support scalar sub-queries.

What is the maximum size of a VARCHAR(MAX) variable?

Maximum size of a VARCHAR(MAX) is 2GB.

What is BCP? When is it used?

It is a tool used to duplicate enormous quantity of information from tables and views. It does not facsimile the structures same as foundation to target. BULK INSERT command helps to bring in a data folder into a record, table or view in a user-specific arrangement.

When is the Explicit Cursor Used ?

If the developer needs to perform the row by row operations for the result set containing more than one row, then he unambiguously declares a pointer with a name. They are managed by OPEN, FETCH and CLOSE.

%FOUND, %NOFOUND, %ROWCOUNT and %ISOPEN characteristics are used in all types of pointers.

How can a SQL Developer prevent T-SQL code from running on a production SQL Server?

Use IF logic with the @@SERVERNAME function compared against a string with a RETURN command before any other logic.

Can you create foreign key constraints on temporary tables?

No: You cannot create a foreign key constraint on temporary tables.

The Hekaton is a new database engine, also known as SQL Server In-Memory OLTP.
Hekaton collaborated with Microsoft Research and released with Microsoft SQL Server 2014.

The Hekaton is a Greek word and meaning is 100 because that newly launched in-memory database which is 100 times faster than the existing SQL Server engine.

If you don’t know about In-memory database, you can visit a below article.

Database Theory: What is In-memory Database?

If we look at traditional RDBMS system, memory resources are expensive, and mostly optimize for disk storage.

The Hekaton allows us to work with memory-optimized tables and indexes which entirely stores in the main memory, and still, we can access via T-SQL like any other regular tables.

We can also create a stored procedure by adding the “WITH NATIVE_COMPILATION” clause that only refers to the memory-optimized tables.

The Hekaton eliminates logical locks using automatic SNAPSHOT ISOLATION with multi-versioning, also having a lock free and latch free structures for accessing the data.

How Hekaton is different than SQL Server standard relational engine?

Very simple answer,

SQL Server standard relational engine developed basically for those data which resides on disk, and it reads and writes 8 KB per data pages which are available in the extents. This process requires lots of CPU I/O and memory internal operations.

With the memory-optimized tables, there are no any data pages and extents. It stores only the data rows into memory with index pointer.

The engine also supports MVCC (Multiversion Concurrency Control) in which same data row has may be the different versions at a time so last updated version accessible by last most requests.

Because of MVCC nature, reader and writer process never block to each other in the Hekaton engine.

What is Multi Version Concurrency Control (MVCC)