[SQL] using pg_tables and tablename in queries
I have a large number of tables with a common naming convention mytable001, mytable002, mytable003 ... mytable00n I would like to do a query across all of the tables, however I do not know all of the tables before hand, and I do not want to ( cant ) manually generate a query like select * from mytable001, mytable002, mytable003 I have a query that returns the names of the tables I want to query: select tablename from pg_tables where tablename like 'mytable%' I have successfully done this query before. I remember it used a odd syntax; I it was something like select * from ( select tablename from pg_tables where tablename like 'mytable%' ) However the above query returns just a listing of tables, I need to use its output in the FROM and treat the input as a table name. ( I've tried creating a Table Function that returns the above set and tried to use that in a select clause, but I cant get it to work. )
Re: [SQL] using pg_tables and tablename in queries
The current behavior is by design.
We use the table as a logging repository. It can get very large
250 000 records. Because of the large number of records that we
have in the table we found it was much faster to perform inserts on a
smaller table. Our current system rolls the tables over
every 12 hours or so, creating a new table with the following behavior:
CREATE TABLE mytable_temp {...}
ALTER TABLE mytable RENAME TO mytable_back_datetime; ALTER TABLE mytable_temp RENAME TO mytable;
I want to join the mytable_back_datetime tables together in order to
perform queries against my huge set of data to generate some
reports. I'm probably going to create a temporary table with a
few indexes to make the reports run faster... however I need to join
the tables all together first.
On 10/4/05, Tom Lane <[EMAIL PROTECTED]> wrote:
solarsail <[EMAIL PROTECTED]> writes:> I have a large number of tables with a common naming convention> mytable001, mytable002, mytable003 ... mytable00n
> I would like to do a query across all of the tables, however I do not know> all of the tables before hand, and I do not want to ( cant ) manually> generate a query like> select * from mytable001, mytable002, mytable003
> I have a query that returns the names of the tables I want to query:> select tablename from pg_tables where tablename like 'mytable%'This looks to me like a situation in which you should rethink your
data design. Those tables should all get merged into one big table,adding one extra column that reflects what you had been using tosegregate the data into different tables.regards,
tom lane
Re: [SQL] using pg_tables and tablename in queries
I managed to make this work as sub query before... I wish I had
written it down somewhere...
Regarding the creation of a function. I do have a function that
almost does that. I'm having a hard time getting it to return a set
of records from the EXECUTE command ( more than one row returned by
the select * ...).
If I generate a temporary table instead of returning the results how
long will that table exist for? Excuse the OOP terminology but would
it be correct to create a 'Singleton' to access the temporary table,
where if it exists and is less than 30 minutes old use that one,
otherwise drop the table and recreate it?
Thanks
-- sample function..
CREATE OR REPLACE FUNCTION testfunc_jointables()
RETURNS SETOF record AS
$BODY$
DECLARE
query TEXT;
BEGIN
query := 'auditrecord';
FOR
atablename IN select * from pg_tables where tablename like
'mytable_%'
LOOP
query := query || ', ' || quote_ident(atablename.tablename);
END LOOP;
EXECUTE ' SELECT * from ' || query;
END;
On 10/4/05, Yasir Malik <[EMAIL PROTECTED]> wrote:
> > The current behavior is by design.
> >
> > We use the table as a logging repository. It can get very large 250 000
> > records. Because of the large number of records that we have in the table we
> > found it was much faster to perform inserts on a smaller table. Our current
> > system rolls the tables over every 12 hours or so, creating a new table with
> > the following behavior:
> >
> > CREATE TABLE mytable_temp {...}
> >
> > ALTER TABLE mytable RENAME TO mytable_back_datetime;
> > ALTER TABLE mytable_temp RENAME TO mytable;
> >
> > I want to join the mytable_back_datetime tables together in order to perform
> > queries against my huge set of data to generate some reports. I'm probably
> > going to create a temporary table with a few indexes to make the reports run
> > faster... however I need to join the tables all together first.
> >
>
> I would create a function that creates a string with a query that includes
> all the tables you need, and call execute on the string. You would loop
> through the all tables from pg_tables and keep on appending the table name
> you need.
>
> Regards,
> Yasir
>
> ---(end of broadcast)---
> TIP 3: Have you checked our extensive FAQ?
>
>http://www.postgresql.org/docs/faq
>
---(end of broadcast)---
TIP 2: Don't 'kill -9' the postmaster
[SQL] query tables based on a query
I have a large number of tables with a common naming convention basically: table001, table002, table003 ... table00n I would like to do a query across all of the tables, however I do not know all of the tables before hand, and I do not want to manually generate a query like select * from table001, table002, table003 I have a query that returns the names of the tables I want to query, it is basically like this: select tablename from pg_tables where tablename like 'table%' How do I do this? I've tried creating a Table Function that returns the above set and tried to use that in a select clause, but I cant get it to work either. Thanks for the help
Re: [SQL] using pg_tables and tablename in queries
Thanks for the help everyone. I got everything working. The query I was orignally looking for was something like this: SELECT * from mytable WHERE pg_tables.tablename IN ( select tablename from pg_tables where tablename like 'mytable _%' ) It turns out that isn't what I really wanted. I now have a nice stored procedure, with a clean interface. Thanks for all the help! On 10/5/05, codeWarrior <[EMAIL PROTECTED]> wrote: > > "Tom Lane" <[EMAIL PROTECTED]> wrote in message > news:[EMAIL PROTECTED] > > solarsail <[EMAIL PROTECTED]> writes: > >> I have a large number of tables with a common naming convention > > > >> mytable001, mytable002, mytable003 ... mytable00n > > > >> I would like to do a query across all of the tables, however I do not > >> know > >> all of the tables before hand, and I do not want to ( cant ) manually > >> generate a query like > > > >> select * from mytable001, mytable002, mytable003 > > > >> I have a query that returns the names of the tables I want to query: > > > >> select tablename from pg_tables where tablename like 'mytable%' > > > > This looks to me like a situation in which you should rethink your > > data design. Those tables should all get merged into one big table, > > adding one extra column that reflects what you had been using to > > segregate the data into different tables. > > > > regards, tom lane > > Sounds like a classic opportunity to use the postgreSQL inheritance model to > me ---(end of broadcast)--- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
