User Defined Data Types in SQL Server?

Question

Are there User Defined Data Types in SQL Server? How can we create and use them?

Answer 1

Creating UTD:

Method#1:

CREATE TYPE PhoneNr FROM VARCHAR(13)
DROP TYPE PhoneNr

Method#2:

sp_addType PhoneNr, 'VARCHAR(13)'
sp_droptype PhoneNr

Usage

CREATE TABLE PersonalInfo ( PersonID INT, PersonNm VARCHAR(100), Phone PhoneNr)