Many DBAs prefer to have “uniqueidentifier” as a table identifier in their data model design over “identity” column. That way DBAs can easily import-export SQL Server tables and data from one database to other database without worrying about uniqueness of the data.

Sometimes you want to import data from external sources during ETL (extract, transform, and load) process and needs to create GUID column on fly and populate data with unique GUIDs. Here is how you do that.

ALTER TABLE Employee
ADD EmployeeID uniqueidentifier null
CONSTRAINT Guid_Default
DEFAULT NEWSEQUENTIALID() WITH VALUES