SQL Server’s Extended Property System: Documenting Your Database
Introduction
Documentation is a critical aspect of database administration and development. It serves not only as a reference guide for understanding database objects and their purposes but also aids in maintaining best practices, ensuring compliance, and simplifying onboarding processes for new team members. Microsoft SQL Server offers a powerful feature for database documentation called the Extended Property system. In this comprehensive article, we’ll delve into what SQL Server’s Extended Property system is, its advantages, how to leverage it for your documentation needs, best practices, and common use cases.
Understanding SQL Server’s Extended Properties
SQL Server’s Extended Properties allow database professionals to add descriptive text, known as metadata, to database objects. This feature is invaluable for recording information such as the description of a table, the purpose of a stored procedure, or the date when an object was last modified. Extended Properties can be associated with various objects, including tables, views, stored procedures, and even columns within a table.
Benefits of Using Extended Properties
- Maintaining clear documentation within the database
- Simplifying database understanding for developers and other stakeholders
- Facilitating database change tracking and history recording
- Improving communication within the team by providing a central source of information
- Enabling metadata accessibility within SQL Server Management Studio as well as other tools
Implementing Extended Properties in SQL Server
Extended Properties can be set, updated, and retrieved through the use of SQL Server built-in system functions such as sp_addextendedproperty, sp_updateextendedproperty, and sp_dropextendedproperty. For retrieving Extended Properties, the function fn_listextendedproperty is utilized.
Adding Extended Properties
EXEC sp_addextendedproperty
@name = N'Description',
@value = N'This table stores customer information.',
@level0type = N'SCHEMA', @level0name = dbo,
@level1type = N'TABLE', @level1name = Customer;
The above T-SQL script adds a description to the Customer table indicating its purpose. The hierarchy of objects is specified through [@leveltype] and [@levelname] arguments, guiding the scope of the property.
Updating Extended Properties
EXEC sp_updateextendedproperty
@name = N'Description',
@value = N'Updated description for this table.',
@level0type = N'SCHEMA', @level0name = dbo,
@level1type = N'TABLE', @level1name = Customer;
This would update the existing ‘Description’ Extended Property for the Customer table to reflect new information.
Deleting Extended Properties
EXEC sp_dropextendedproperty
@name = N'Description',
@level0type = N'SCHEMA', @level0name = dbo,
@level1type = N'TABLE', @level1name = Customer;
With the command provided, you can remove an Extended Property that’s no longer needed or has become obsolete.
Viewing Extended Properties
SELECT
[name],
[value]
FROM
fn_listextendedproperty (
NULL,
'SCHEMA', 'dbo',
'TABLE', 'Customer',
NULL, NULL);
To view the Extended Properties for the Customer table, you might use the code snippet above. This reveals the name and value of any Extended Properties associated with that table.
Best Practices for Using Extended Properties
Implementing Extended Properties comes with its set of best practices to ensure that documentation remains organized, consistent, and useful:
- Consistency in Naming: Always adhere to a consistent naming convention for the Extended Properties names.
- Detailed Descriptions: Ensure that descriptions are detailed and informative.
- Regular Updates: Update Extended Properties to reflect any changes made to the database objects.
- Avoid Redundancy: Avoid adding properties that are self-explanatory or redundant.
- Central Management: Consider using a script or tool to centrally manage Extended Properties.
Extended Properties in SQL Server Management Studio (SSMS)
SQL Server Management Studio provides a user-friendly interface to work with Extended Properties. You can access Extended Properties directly within the object’s properties dialog box in SSMS. For example, tables, columns, and other objects have a ‘Properties’ option when right-clicked in the Object Explorer, which brings up a window where you can manage the Extended Properties without needing to write SQL statements.
Automating Documentation with Extended Properties
Extended Properties play a crucial role when automating database documentation. Scripts and third-party tools can extract Extended Properties to generate reports or web pages, providing a dynamic and refreshing take on conventional database documentation. In addition, through integration with version control systems, Extended Properties can be included in source control, ensuring that documentation evolves alongside the database schema.
Common Use Cases for Extended Properties
Extended Properties can be used for a variety of purposes, including:
- Indicating the version number of a database or table
- Logging the purpose of code blocks in stored procedures or functions
- Marking deprecated objects that shouldn’t be used anymore
- Documenting the data lineage of columns, showcasing the flow of data from source to target
- Maintaining an audit trail for changes to database design or structure
Conclusion
SQL Server’s Extended Property system presents a powerful and versatile toolset for comprehensive database documentation, serving as a cornerstone for data governance, team collaboration, and maintaining data integrity. By following the methods and best practices outlined in this article, you can utilize Extended Properties to accurately document and effectively communicate the structure and purpose of your database elements within your organization, making your databases more transparent, maintainable, and reliable.
References and Further Reading
For further exploration of SQL Server’s Extended Properties and database documentation strategies, consider consulting the following resources:
- Microsoft Docs on SQL Server Extended Properties
- SQL Server Management Studio Documentation
- Professional books and academic papers on database administration
- Online courses and tutorials on SQL Server
- Community forums and discussion boards related to SQL Server
