List User-Defined Types (UDTs) in Your SQL Server Database: A Beginner's Guide

UDTs are custom data types you can create in addition to the built-in types offered by SQL Server. They help enforce data structure and consistency within your database.

Methods for Listing UDTs:

Using SQL Server Management Studio (SSMS):

This method is the easiest and most visual approach.

• Expand User-defined types. This folder will list all the UDTs you have created in the database.
• Underneath Types, you'll see two subfolders: System data types (predefined types) and User-defined types.
• Expand the Types folder.
• Expand the Programmability folder.
• In Object Explorer, navigate to your database.
• Open SSMS and connect to your SQL Server database.

Using T-SQL Query:

You can also list UDTs using a Transact-SQL (T-SQL) query. Here's an example:

SELECT 
    t.name AS type_name,
    s.name AS schema_name,
    t.is_user_defined
FROM sys.types AS t
INNER JOIN sys.schemas AS s ON t.schema_id = s.schema_id
WHERE t.is_user_defined = 1;

Explanation of the query:

• WHERE t.is_user_defined = 1: Filters the results to only show user-defined types (where is_user_defined is 1).
• INNER JOIN: This clause joins the sys.types and sys.schemas views based on the schema_id to include the schema information.
• SELECT: This clause specifies the columns you want to retrieve.
  • t.name AS type_name: Gets the name of the user-defined type and renames it to "type_name" for readability.
  • s.name AS schema_name: Gets the name of the schema where the UDT is defined and renames it to "schema_name".
  • t.is_user_defined: Checks if the type is user-defined (value 1) or not.
• sys.schemas: This system view contains information about schemas in the database.
• sys.types: This system view contains information about all data types, including user-defined ones.

This query will list the names of all UDTs in your database, along with the schema they belong to.

Related Issues and Solutions:

• Filtering by specific schema: If you want to list UDTs from a specific schema, modify the query by adding a WHERE clause like: WHERE s.name = 'MySchemaName'.
• Missing sys.types view: This view is available in SQL Server 2005 and later versions. If you're using an earlier version, you can use the sysobjects view with caution, as it includes system types as well.