Question : Converting Integer Identity Columns to Character columns

SQL Server 2000

We have a system with two main IDs which exist in many tables - BaseID and SecondaryID.

Right now, they are currently Integer values (IDENTITY in the main table).  It has been requested that a distinction be made between the two, for example:

a BaseID of 2000 could be confused with a SecondaryID of 2000.  So the first could be BAS2000, and the second SEC2000.

Is it appropriate to make this change at the database level ?  It would require more administration to maintain character fields as opposed to IDENTITY Integer fields.

If so, how should it be done ?

Thanks,
JK

Answer : Converting Integer Identity Columns to Character columns

Another possibility:
You could use a computed column that added the string prior to display but did *not* store the string in the table.  Within that approach, you have two methods; which is easier depends on how the code is currently written.

1) Make the computed column names the same as the existing column names; the column name will be the same, although the datatype will change (from int to varchar).  Naturally that requires renaming the existing columns.
2) Make the computed column a new name that is used only for display.

1)
-- rename the existing columns so that the new computed columns can have the same name as
-- the previous ID columns, reducing the changes that must be made to application code
EXEC sp_rename 'tableName.BaseID', 'BaseIDNumber', 'COLUMN'
EXEC sp_rename 'tableName.SecondaryID', 'SecondaryIDNumber', 'COLUMN'
-- add computed columns, with needed prefixes, that take the place of the original columns
ALTER TABLE tableName
    ADD BaseID AS 'BAS' + CAST(BaseIDNumber AS VARCHAR(10))
ALTER TABLE tableName
    ADD SecondaryID AS 'SEC' + CAST(SecondaryIDNumber AS VARCHAR(10))


2)
-- add new computed columns used for display only
ALTER TABLE tableName
    ADD BaseIDDisplay AS 'BAS' + CAST(BaseID AS VARCHAR(10))
ALTER TABLE tableName
    ADD SecondaryIDDisplay AS 'SEC' + CAST(SecondaryID AS VARCHAR(10))