Re: double linked list

From: DA Morgan <>
Date: Wed, 05 Feb 2003 17:16:32 -0800
Message-ID: <>

--CELKO-- wrote:

> <snipped>columns are indexed, it is reasonably fast. <<
> >> What do you mean by "direct use"? This is SQL, a user is allowed to
> inline and nest subqueries. <<
> But you want to avoid them in favor of simple, "flat" joins whenever
> possible. They hurt performance and maintainability.

Not in Oracle.

The performance impact of inline views, while there must be some, is unmeasurable. And, in fact, I can easily demonstrate cases where subqueries are substantially faster than flat joins and do so in the EXPLAIN PLAN lesson I teach first quarter students.

Maintainability depends on what developers are used to working with. If you haven't seen curly braces before they are a nightmare. In the case of serious Oracle shops ... inline views and nested subqueries are so common as to have no impact on maintainance.

PL/SQL and the optimizer have changed a lot recently. Knowledge of how things worked three to five years ago, or more, is nearly useless.

Daniel Morgan Received on Thu Feb 06 2003 - 02:16:32 CET

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