Re: Getting the column to a which a sequence belongs.

On Thu, Aug 27, 2009 at 09:18:57PM +0200, Thomas Kellerer wrote:
> I'm trying to extend the Postgres support in my SQL tool. I'm trying to
> recreate the SQL for a sequence, and I wonder if there is a way to find
> out the column to which a sequence "belongs".

The information is all in the system catalogs; I've not had much
opportunity to fiddle with them so far but the following may be a start
to help get things out for you.

  SELECT c.relname, a.attname, t.relname
  FROM pg_class c, pg_depend d, pg_class t, pg_attribute a
  WHERE c.relkind     = 'S'
    AND d.objid       = c.oid
    AND d.refobjid    = t.oid
    AND (d.refobjid,d.refobjsubid) = (a.attrelid,a.attnum);

The first reference to "pg_class" can probably be dropped as you can
convert the names of tables/sequences into their oid by using literals
of type "regclass".  For example, to pull out all the column names from
table "foo", you can do:

  SELECT attname
  FROM pg_attribute
  WHERE attrelid = 'foo'::regclass;

Have a look here for docs:

  http://www.postgresql.org/docs/current/static/catalogs.html

--
  Sam  http://samason.me.uk/