Re: Best way to allow column to initially be null?

Glen Huang wrote:
> I’m trying to make a column have these properties:
>
> 1. When a row is inserted, this column is allowed to be null. 2. When the row is updated, no null
> can be assigned to it this column.
>
> I initially thought I can drop the not null constraint before insertion and turn it back on after
> that, but after reading the doc it seems turning on not null constraint requires not columns
> contain null value, so looks like it won’t work.
>
> My current approach is to not set the not null constraint in the table and use a before update
> trigger to manually raise exception when the column is null. But it doesn’t seem as elegant.
>
> Is there a better way?
>

Sounds to me like a BEFORE UPDATE trigger is exactly the way to handle this. Rejecting invalid data
input values is an ideal use case for such a facility.