modifying a column in the table

[sowmyav]

Hi,
I would like to add new fields(column) in the already existing table in SQL server mangement studio.2005
When I added the needed fields,I want to use the check constraint to check the 2 fields namely
PROD_STATUS char(10) IN or OUT
ANAL_FLAG char(10) YES or NO
it should have only the above mentioned values in the table.So could any please let me know how to proceed on the same as I am getting the error as
follows:
'SYS_200812' table
- Unable to modify table.
Cannot insert the value NULL into column 'PROD_STATUS', table 'AS.dbo.Tmp_SYS_200812'; column does not allow nulls. INSERT fails.
The statement has been terminated.


'SYS_200812' table
- Unable to modify table.
ALTER TABLE only allows columns to be added that can contain nulls, or have a DEFAULT definition specified, or the column being added is an identity or timestamp column, or alternatively if none of the previous conditions are satisfied the table must be empty to allow addition of this column. Column 'PROD_STATUS' cannot be added to non-empty table 'SYS_200812' because it does not satisfy these conditions.