Create table as subquery performance

From: Bruce Douglas <bruce.douglas_at_bridge.bst.bls.com>
Date: 1996/10/23
Message-ID: <326E7A80.1725_at_bridge.bst.bls.com>#1/1

I'm using a reporting tool that makes extensive use of Oracle's CREATE TABLE X AS SELECT * FROM Y syntax. I'm tracking down a performance problem and have discovered this:

CREATE TABLE X AS SELECT * FROM Y takes much longer than breaking the process into pieces:

	CREATE TABLE X;
	INSERT INTO X SELECT * FROM Y;

In the trivial example I'm testing, the elapsed time drops from 6 minutes to 5 seconds.

Can someone point me in the right direction? What's going on here?

As always, thanks in advance for your help.

---

Bruce Douglas -- bruce.douglas_at_bridge.bst.bls.com BellSouth Telecommunications

---

Received on Wed Oct 23 1996 - 00:00:00 CEST