The uniqueidentifier data type in SQL Server is used to store globally unique identifiers (GUIDs) that are generated by using the NEWID() function. A GUID is a 128-bit number that is guaranteed to be unique across all computers and networks.
Creating a table with a uniqueidentifier column:
To use the uniqueidentifier data type, you need to create a table with a column of this data type. Here’s an example:
CREATE TABLE MyTable ( ID uniqueidentifier, Name varchar(50) )
In this example, we created a table called MyTable with two columns – ID and Name. The ID column is of type uniqueidentifier, which will store the GUID values.
Inserting values into the uniqueidentifier column:
To insert values into the ID column of type uniqueidentifier, you can use the NEWID() function. The NEWID() function generates a new GUID every time it’s called.
INSERT INTO MyTable (ID, Name) VALUES (NEWID(), 'John Doe')
In this example, we inserted a new row into the MyTable table with a randomly generated GUID as the ID and ‘John Doe’ as the Name.
Querying rows based on the uniqueidentifier value:
When querying rows based on the uniqueidentifier value, you can use the WHERE clause along with the comparison operator (=). For example:
SELECT * FROM MyTable WHERE ID = '8B0297F2-4C76-4B1A-B9D6-8E2C5E51E6D7'
In this example, we selected all rows from MyTable where the ID is equal to ‘8B0297F2-4C76-4B1A-B9D6-8E2C5E51E6D7’.
When working with the uniqueidentifier data type, here are some best practices to keep in mind:
– Always use the NEWID() function to generate new GUIDs when inserting values into a uniqueidentifier column. – Avoid using string literals to compare with uniqueidentifier values.
Instead, convert the string literal to a uniqueidentifier using the CAST or CONVERT function. – If you need to generate sequential GUIDs, you can use the NEWSEQUENTIALID() function instead of NEWID(). However, keep in mind that sequential GUIDs are not guaranteed to be globally unique.
- INSERT INTO MyTable (ID, Name) VALUES (NEWSEQUENTIALID(), ‘Jane Smith’)
In this tutorial, we learned how to use the uniqueidentifier data type in SQL Server. We saw how to create a table with a uniqueidentifier column, insert values into this column using the NEWID() or NEWSEQUENTIALID() functions, and query rows based on the uniqueidentifier value. We also discussed some best practices when working with this data type.
Now that you have a good understanding of how to use the uniqueidentifier data type, you can start incorporating it into your own SQL Server projects.