Обсуждение: Re: Need some help converting MS SQL stored proc to postgres function

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

Mike Christensen wrote:
> Hi guys, I'm in the process of migrating my database from MS SQL 2005
> to PostgreSQL and there's one final stored proc that's giving me some
> problems..  Perhaps someone can give me some help?  Here's the sproc:
>
>  SELECT
>    RecipeId, Avg(Rating) as Rating
>  INTO #ratings
>  FROM RecipeRatings GROUP BY RecipeId
>
>  UPDATE Recipes
>    SET Rating = #ratings.Rating FROM Recipes INNER JOIN #ratings ON
> (#ratings.RecipeId = Recipes.RecipeId AND #ratings.Rating <>
> Recipes.Rating)
>
>  DROP TABLE #ratings
>
> The error is:
>
> ERROR:  syntax error at or near "#"
> LINE 3:   INTO #ratings
>               ^
>
> ********** Error **********
>
> ERROR: syntax error at or near "#"
> SQL state: 42601
> Character: 53
>
> Perhaps there's a different way to create temp tables?  Even better is
> if someone can re-write the query to not use the temp table, I'm far
> from a SQL expert.  Thanks!!
>
> Mike
>

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