| From: | Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com> |
|---|---|
| To: | Kenneth Gonsalves <lawgon(at)thenilgiris(dot)com> |
| Cc: | Richard Huxton <dev(at)archonet(dot)com>, weberp(at)paradise(dot)net(dot)nz, pgsql-sql(at)postgresql(dot)org |
| Subject: | Re: Query performance problem |
| Date: | 2005-03-18 13:19:28 |
| Message-ID: | 20050318051614.Q61964@megazone.bigpanda.com |
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| Thread: | |
| Lists: | pgsql-sql |
On Fri, 18 Mar 2005, Kenneth Gonsalves wrote:
> On Thursday 17 Mar 2005 7:35 pm, Richard Huxton wrote:
>
> > Not necessarily. NOT NULL here helps to ensure you can add values
> > together without the risk of a null result. There are plenty of
> > "amount" columns that should be not-null (total spent, total
> > ordered etc).
>
> that makes sense - but is it necessary to have a not null constraint
> when there is a default value?
It's also an added check which prevents you from explicitly setting the
value to NULL in an insert or update, since
"insert into foo(col1) values (NULL);" shouldn't insert the default value
into col1. This is relatively minor generally, but if you have queries
whose behavior is broken by NULLs (things using IN/NOT IN for example)
it's better to be safe.
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