What Data Type Is GUID in SQL Server?
In SQL Server, a Globally Unique Identifier (GUID) is a data type used to store a unique identifier value. It is represented as a 16-byte binary data type. GUIDs are typically used when you need to generate unique identifiers across different systems or databases.
Advantages of using GUIDs
GUIDs offer several advantages over other identifier types:
- Uniqueness: GUIDs are designed to be globally unique, meaning the probability of generating duplicate values is extremely low.
- No central authority required: Unlike identity columns or sequences, GUIDs can be generated independently without relying on a central authority.
- Ease of replication: GUIDs can be easily replicated across different databases or systems without the need for coordination.
Creating and inserting GUID values
To create and insert GUID values into a SQL Server table, you can use either the NEWID() function or the NEWSEQUENTIALID() function. Here’s an example:
CREATE TABLE MyTable ( Id UNIQUEIDENTIFIER DEFAULT NEWID(), Name VARCHAR(50) ) INSERT INTO MyTable (Name) VALUES ('John Doe')
The above code creates a table called “MyTable” with an “Id” column of type UNIQUEIDENTIFIER. The default value for the “Id” column is generated using the NEWID() function, which generates a unique identifier. The INSERT statement then inserts a row into the table with the name ‘John Doe’ and an automatically generated GUID value.
Querying GUID values
When querying tables with GUID columns, you can use the standard comparison operators (=, <>, <, >, etc.) to filter and retrieve specific rows. Here’s an example:
SELECT * FROM MyTable WHERE Id = '3F2504E0-4F89-11D3-9A0C-0305E82C3301'
The above query retrieves all rows from the “MyTable” table where the “Id” column matches the specified GUID value.
In SQL Server, the GUID data type provides a reliable way to generate and store unique identifiers. Its advantages include global uniqueness, independence from central authorities, and easy replication across systems. By understanding how to create, insert, and query GUID values in SQL Server, you can effectively utilize this data type in your database applications.