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.
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