Online Documentation for SQL Administrator for SQL Server
Data Type Editor
Use the Data Type Editor to create an alias data type or a user-defined type in the current database in SQL Server Database. The implementation of an alias data type is based on a SQL Server native system type. A user-defined type is implemented through a class of an assembly in the Microsoft .NET Framework common language runtime (CLR).
UDT Editor allows you to define user-defined type properties. It opens automatically when you create a new type and is available on editing an existing one.
To open a user-defined type in UDT Editor, double-click it in Data Types list.