Glen Huang wrote:> I’m trying to make a column have these properties:>> 1. When a row is inserted, this column is
allowedto be null. 2. When the row is updated, no null> can be assigned to it this column.>> I initially thought I can
dropthe not null constraint before insertion and turn it back on after> that, but after reading the doc it seems
turningon not null constraint requires not columns> contain null value, so looks like it won’t work.>> My current
approachis to not set the not null constraint in the table and use a before update> trigger to manually raise exception
whenthe 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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