Re: [Fwd: SQL3 recursive unions]

From: Michael Meskes <meskes(at)postgresql(dot)org>
To: Ron Peterson <rpeterson(at)yellowbank(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [Fwd: SQL3 recursive unions]
Date: 2000-06-17 12:17:23
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On Thu, Jun 15, 2000 at 03:58:40PM -0400, Ron Peterson wrote:
> PostgreSQL's TODO list ( makes
> reference to implementing SQL3 recursive queries. Where does this task
> fall in the overall priority of things? I hate to just whine without

I want to implement this for some years now. But I haven't found the time to
even start yet.

> offering to help, but I think this would be a rather big bite to chew.
> (Actually, I would be happy to help, if anyone had any suggestions about
> what I might be able to do)

So at least we are two who are interested in this.

> Here's an example from DB2's documentation, cleaned up a bit:

Is this SQL3 syntax?

> with rpl (part, subpart, quantity) as
> (
> select root.part, root.subpart, root.quantity
> from partlist root
> where root.part = '01'
> union all
> select child.part, child.subpart, child.quantity
> from rpl parent, partlist child
> where parent.subpart = child.part
> )

Hmm, this doesn't look correct. What if a subpart is used by different
parts? I think the second query needs an aggregate.

But the above query certainly does solve the ancestor problem.

Does anyone have an idea how DB2 executes such a statement?

Michael Meskes
Go SF 49ers! Go Rhein Fire!
Use Debian GNU/Linux! Use PostgreSQL!

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