Creating User Defined Types in Sql Server

Sql Server User Defined Types are used to enforce consostency in table definition.

Also you can use User Defined Type to create new data types that do not exist in the Sql Server.

Use the following command to create UDT:

CREATE TYPE UDT_COUNTRY FROM nvarchar(30) NOT NULL;

The UDTs are always created based on Sql Server data types. You could then use this USER DEFINED TYPE when you are defining a table.

CREATE TABLE Employee

(

          Employee_Id   int,

          First_Name     nvarchar(256),

          Last_Name     nvarchar(256),

          Address                  nvarchar(512),

          City              nvarchar(30),

          Country                  UDT_COUNTRY

);

The UDT will be diplayed as "UDT_COUNTRY:nvarchar(30)" or Country(UDT_COUNTRY(nvarchar(30))) in the table definition window of Sql Server.