[Tutor] updating databases with null values

bob gailer bgailer at gmail.com
Thu Dec 9 18:34:15 CET 2010

On 12/9/2010 11:46 AM, Rance Hall wrote:
> I have a set of questions that ask about a customers name, address, email, etc.
> some of these values are allowed to be null, and others aren't.  Some
> are required to have specific formats when they aren't null.
> I'm happy with the code Ive written and its question asking routine,
> but I need help understanding how best to deal with null values.
> I'm connecting to a postgres database with the python postgres module
> described here: http://python.projects.postgresql.org/
> I'm also using python 3.x if it matters.
> The sql is different if you want to allow null values
> update table set value = "string" where condition
> with null value:
> update table set value = NULL where condition
> It would seem I need several iterations of the prepared db statement
> for various combinations of null values or I don't allow null values
> at all and put empty strings in the database instead of the null

Offhand I'd say you could use a parameterized stattement, like

update table set value = ? where condition

Then pass either the string or NULL when executing. I don't know 
postgresql's exact way to do this.

> value.
> Could someone help me think through this idea and help me decide on a
> good method.  Right now I'm thinking that I should skip null values
> and just store zero length strings in the db.  I don't like it, but
> its certainly much easier (at least to me so far)
> Your thoughts?
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Bob Gailer
Chapel Hill NC

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