Uniqueidentifier Data Type – SQL Server

 In SQL Server, the uniqueidentifier data type is a 16-byte GUID (Globally Unique Identifier) that is used to uniquely identify rows in a table. This data type can be useful in scenarios where you need to ensure that each row in a table has a unique identifier. In this blog, we will explore the uniqueidentifier data type in SQL Server and provide a sample use case.

Introduction to the uniqueidentifier data type

The uniqueidentifier data type is a fixed-length data type that can store a 128-bit GUID. A GUID is a unique identifier that is generated using an algorithm that ensures that the identifier is globally unique. The uniqueidentifier data type can be useful in scenarios where you need to create a unique identifier for each row in a table, such as in a customer database where you need to ensure that each customer has a unique identifier.

Creating a table with a uniqueidentifier column

To create a table with a uniqueidentifier column, you can use the following code:

CREATE TABLE MyTable

(

  ID uniqueidentifier PRIMARY KEY,

  Name varchar(50)

);

Inserting data into a table with a uniqueidentifier column

To insert data into a table with a uniqueidentifier column, you can use the "NEWID()" function to generate a new GUID. The following code inserts a row into the MyTable table with a new uniqueidentifier:

INSERT INTO MyTable (ID, Name)

VALUES (NEWID(), 'John Doe');

Querying data from a table with a uniqueidentifier column

Once you have data stored in a table with a uniqueidentifier column, you can query the data using SQL Server's built-in functions. For example, you can use the "WHERE" clause to select rows with a specific ID value. The following code selects the row from the MyTable table with the ID value "D26749F6-A152-41FC-A3C9-2D8A743048D5":

SELECT *

FROM MyTable

WHERE ID = 'D26749F6-A152-41FC-A3C9-2D8A743048D5';

 

Sample use case

Let's say you are working on a project that requires you to create a database of customer information. Each customer must have a unique identifier that is used to identify the customer throughout the system. In this scenario, you can use the uniqueidentifier data type to create a unique identifier for each customer.

You can create a Customers table with a uniqueidentifier column that is used to store the unique identifier for each customer:

CREATE TABLE Customers

(

  ID uniqueidentifier PRIMARY KEY,

  FirstName varchar(50),

  LastName varchar(50),

  Email varchar(100)

);

When a new customer is added to the database, you can generate a new GUID using the "NEWID()" function and insert it into the ID column:

INSERT INTO Customers (ID, FirstName, LastName, Email)

VALUES (NEWID(), 'John', 'Doe', 'johndoe@example.com');

Now, each row in the Customers table has a unique identifier that can be used to identify the customer throughout the system.

Conclusion

The uniqueidentifier data type in SQL Server is a useful tool for creating unique identifiers for rows in a table. It can be used in a variety of scenarios, such as in a customer database where you need to ensure that each customer has a unique identifier. By using the uniqueidentifier data type and the "NEWID()" function, you can easily create and manage unique identifiers in your SQL Server applications.