SQL SERVER - What is user defined data type, and how to create

 It is very esay dont worry about how to use and create it below example just run only. 

It allows defining its own T- SQL User Defined Data Type and you can use this UDDT to entire Database.

See the following example-

-- TO CREATE USER DEFINED DATA TYPE WITH VARCHAR DATA TYPE

EXEC SP_ADDTYPE TYPE1, 'VARCHAR(50)','NULL'

-- TO CREATE USER DEFINED DATA TYPE WITH INT DATA TYPE 

--Example 2 (run this Full Script)

EXEC SP_ADDTYPE  @TYPENAME =TYPE2,

@PHYSTYPE= INT,

@NULLTYPE=NULL,

@OWNER= DBO

-- Declare the variable and data type is 'TYPE2'

DECLARE @MYVARIALBE TYPE2

-- Set the value in vairaible

SET @MYVARIALBE = 100

-- Get the value from varaible

SELECT @MYVARIALBE AS MYVALUE

-- Drop user defined data type

Drop  type  TYPE2