sql- Alter table to add a column which default value is based on other value

Question

my sql table:

  CREATE TABLE [dbo].[PayrollParameter]
  (
     [PayrollParameterID]  [CHAR](36) NOT NULL,
     [Description]         [NVARCHAR](50) NOT NULL,
     [NumberOfDaysInMonth] [INT] NOT NULL,
     [IsFixedDaysInMonth]  [BIT] NOT NULL,
     CONSTRAINT [PK_PayrollParameter] PRIMARY KEY CLUSTERED (
     [PayrollParameterID] ASC )WITH (pad_index = OFF, statistics_norecompute =
     OFF, ignore_dup_key = OFF, allow_row_locks = on, allow_page_locks = on) ON
     [PRIMARY]
  )
 ON [PRIMARY]
 GO 

the database already contain records; I want to alter the table to set the default value of IsFixedDaysInMonth to Checked if NumberOfDaysInMonth!=0

How can i do this?

Answer 1

CREATE DEFAULT needs a constant value as the default

Is an expression that contains only constant values (it cannot include the names of any columns or other database objects).

The only ways I know to do what you want would be to use a trigger or insert using a stored procedure.