Re: Auto-updated fields

On Thu, May 08, 2008 at 08:44:46AM +0200, Martijn van Oosterhout wrote:
> On Wed, May 07, 2008 at 03:04:49PM -0700, David Fetter wrote:
> > 1.  Create a generic (possibly overloaded) trigger function,
> > bundled with PostgreSQL, which sets a field to some value.  For
> > example, a timestamptz version might set the field to now().
> 
> Doesn't the SQL standard GENERATED BY functionality work for this?
> Or won't that handle updates?

It appears to, at least according to 6WD2_02_Foundation_2007-12.pdf :)

4.14.8 Base columns and generated columns
   A column of a base table is either a base column or a generated   column. A base column is one that is not a
generatedcolumn. A   generated column is one whose values are determined by evaluation   of a generation expression, a
<valueexpression> whose declared   type is by implication that of the column. A generation expression   can reference
basecolumns of the base table to which it belongs   but cannot otherwise access SQL data.  Thus, the value of the field
 corresponding to a generated column in row R is determined by the   values of zero or more other fields of R.  A
generatedcolumn GC   depends on each column that is referenced by a <column reference>   in its generation expression,
andeach such referenced column is a   parametric column of GC.
 

Cheers,
David.
-- 
David Fetter <david@fetter.org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david.fetter@gmail.com

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