Re: Does Oracle create temporary indexes for sub queries?

Dean wrote:

> if this were a typical thing that people either add to their subqueries or not.

More typically they would add hints, specify plan stability, or tell the optimizer about known skews. It is not generally a good idea to expect syntax to force any particular optimization. Futzing with the syntax made some sort of sense sometimes when the optimizer followed a few simple rules, but that no longer applies. The general way of doing it these days is to properly design your system according to relational algebra, write your code to solve specific business problems in the design, then use tools such as explain plan and tracing to explicate any potential performance problems.

See the documentation on how the CBO works, google for explanations on how the CBO works, read anything by Tom Kyte, Cary Milsap or Jonathan Lewis (no disrespect intended to any not named here). I also still like Lawson's book for a beginner's "how-to-dba."

jg

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