What Data Type Is Uniqueidentifier SQL Server?


Angela Bailey

What Data Type Is Uniqueidentifier SQL Server?

In SQL Server, the uniqueidentifier data type is used to store a 16-byte globally unique identifier (GUID). A GUID is a unique value that is generated by the computer’s network card or other hardware devices and is guaranteed to be unique across all devices and all time.

Properties of Uniqueidentifier Data Type

  • A uniqueidentifier column can store values in the format ‘xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx’, where each x represents a hexadecimal digit (0-9 or A-F).
  • The value of a uniqueidentifier is not sequential or incremental. It does not provide any information about the order in which the rows were inserted into a table.

Generating Uniqueidentifiers

To generate a new uniqueidentifier in SQL Server, you can use the NEWID() function. This function returns a new globally unique identifier each time it is called.



You can also assign a specific value to a uniqueidentifier column using the following syntax:


INSERT INTO TableName (UniqueColumn) VALUES ('xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx')

Working with Uniqueidentifiers

The uniqueidentifier data type is commonly used when you need to uniquely identify rows in tables or when you need to generate primary keys for your records. It can be particularly useful when working with distributed databases or when integrating with external systems.

If you want to compare two uniqueidentifiers for equality, you can use the = operator:


SELECT * FROM TableName WHERE UniqueColumn = 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'

You can also order the results by a uniqueidentifier column using the ORDER BY clause:


SELECT * FROM TableName ORDER BY UniqueColumn


The uniqueidentifier data type in SQL Server is a powerful tool for uniquely identifying records and generating primary keys. It provides a globally unique identifier that can be used across different systems and ensures uniqueness even in distributed environments.

By understanding the properties and usage of the uniqueidentifier data type, you can leverage its capabilities to improve your database design and data management in SQL Server.

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