SELECT a value from various tables depending on a column value - Mailing list pgsql-general

From Eric E
Subject SELECT a value from various tables depending on a column value
Date
Msg-id 41829814.8070808@bonbon.net
Whole thread Raw
Responses Re: SELECT a value from various tables depending on a column  (Paul Tillotson <pntil@shentel.net>)
List pgsql-general
Hi,
    I'm trying to write a recordset-returning function that returns a
values from a base table, and one column from a joined table, where the
joined table varies according to a field of the base table.  I'm looking
for an efficieint way to do this, and I don't think I know enough about
Postgres' capabilities to know how to do this.

I imagine fetching my base table rows in order of the table reference
column, looping over my base table, and setting a refcursor to a new
joined table when the table reference column changes.  I would then
fetch from the appropriate joined table cursor to get the joined value
for each row.

So my question is a performance one: is this a sensible way to do this,
or am I missing something altogether about hierarchies of tables.

Or can I fetch a bunch of rows into memory and loop over them there,
thus avoid queries to look up individual rows over and over.

Any ideas would be much appreciated.

Many thanks,

Eric


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