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

Good to know I’m not doing something stupid. Thanks.

> On 30 Sep 2017, at 8:51 PM, Berend Tober <btober(at)computer(dot)org> wrote:
>
> 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.