Re: Update on Insert

> -----Original Message-----
> From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-
> owner@postgresql.org] On Behalf Of Sebastian Feher
> Sent: Monday, November 16, 2009 10:41 AM
> To: pgsql-general@postgresql.org
> Subject: [GENERAL] Update on Insert
>
> Hi Everyone,
>
> Given a table "Items" with a PK "item1" and "Qty" - a numeric column
> I'd like to define a way in Postgres to insert when item11 doesn't
> exist already in "Items" and update the Qty by adding the new quantity
> to the existent when the item11 exists. What is a good approach and
> where should I be looking for details. Thanks.

That is called MERGE.  Merge is not currently supported:
http://www.postgresql.org/docs/8.4/interactive/unsupported-features-sql-
standard.html

You could set the transaction level to Serializable, start a
transaction, check for existence, if the row exists perform an update,
else perform an insert. Then commit.