if exists (select * from ::fn_listextendedproperty('MS_Description', 'schema', 'dbo', 'table', 'EMPLOYEE', 'column', 'EMP_NUM'))
BEGIN
exec sys.sp_dropextendedproperty 'MS_Description', 'schema', 'dbo', 'table', 'EMPLOYEE', 'column', 'EMP_NUM'
END
exec sys.sp_addextendedproperty 'MS_Description', 'DESCRIPTION OF THE COLUMN.', 'schema', 'dbo', 'table', 'EMPLOYEE', 'column', 'EMP_NUM'
go