On Sun, 01 Feb 2009 00:10:52 -0800
Mike Christensen <imaudi@comcast.net> wrote:
> Figured out one way to do it, perhaps I can get some feedback on
> if this is the best way.. Thanks!
>
> CREATE TEMP TABLE temp_ratings
> (
> RecipeId uuid,
> Rating smallint,
> CONSTRAINT id_pk PRIMARY KEY (RecipeId)
> );
>
> INSERT INTO temp_ratings(RecipeId, Rating)
> SELECT RecipeId, Avg(Rating) as Rating FROM RecipeRatings GROUP
> BY RecipeId;
>
> UPDATE Recipes
> SET Rating = tr.Rating
> FROM temp_ratings as tr
> WHERE Recipes.RecipeId = tr.RecipeId AND Recipes.Rating <>
> tr.Rating
You can have a similarly coincise form using
insert into temp table
http://www.postgresql.org/docs/8.3/interactive/sql-selectinto.html
check what temporary table really means regarding transactions,
functions and connections.
[1]
http://www.postgresql.org/docs/8.3/interactive/sql-createtable.html
If specified, the table is created as a temporary table. Temporary
tables are automatically dropped at the end of a session, or
optionally at the end of the current transaction (see ON COMMIT
below). Existing permanent tables with the same name are not visible
to the current session while the temporary table exists, unless they
are referenced with schema-qualified names. Any indexes created on a
temporary table are automatically temporary as well. Optionally,
GLOBAL or LOCAL can be written before TEMPORARY or TEMP. This makes
no difference in PostgreSQL, but see Compatibility.
of course depending on the context it may be useful to use "on
commit" that seems to be only supported by the "more verbose" create
path.
Still the create path offer some shortcut to avoid to specify the
schema of the temp table.
create table like [1]
and create table as that seems the most promising for your needs
http://www.postgresql.org/docs/8.3/interactive/sql-createtableas.html
not everything is yet as we dream it, but there is still a lot of
syntactic sugar available to exploit.
--
Ivan Sergio Borgonovo
http://www.webthatworks.it