The Senior […] does not even have the time […] the Junior then decides to try out different things It is also a book about em. And about 12c. No mention of 12cR2, which is massively more performant. I have been using 12c for about one year and multiple topics are covered.
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Plus, as a database administrator, I always have this bad conscience about not being fluent enough in SQL What way round did it work again, connect by? So I thought, I might as well get the book and write a review. Unfortunately for me, as I do not like to criticize other people, this review will not be positive, and I was quite unsure should I really do it. Now let me start with something positive: I do like the intended focus on creativity.
One terminological thing that bothers me may be a subjective reaction, possibly even related to my not being a native English or American speaker. If it is different, we consider what we have found a new, distinct workaround; otherwise, we have only found a workaround equivalent to one of the other workarounds, which we also refer to as a synonymous workaround.
In other words, things mean the same because they are executed the same way? This is a severe category error and must be incredibly confusing and frustrating! Say I rewrite my query completely, and still I get the same execution plan, — really?
And then I execute it on another system, where a different Oracle version is running, and the plan is totally different? Nothing, as far as this book is concerned. In the predictive, explain plan style execution plans displayed in the book, all I may consider is the cost — may I rely on that?
But choosing among different plans is not addressed by the author guess I just execute and time the queries in my development environment ;-. All that is addressed is how to enlarge my set of equivalent formulations. Now, had the author just been content with showing different ways of writing SQL queries, not mixing in execution plans and pseudo-theoretic jargon, all would have been better or at least less confusing.
But given the author does show the explain plan for just about every rephrasing, at least he should have made some global comments about how these plans differ in general. But in the book, plans where a scan of some table is executed for every row of another table are not treated any different from plans where every table is scanned once — no ranking of plans, no comment, no nothing. In a nutshell what this book does wrong is, in my opinion, to promote some sort of mechanical creativity while not providing insight.
How do I get a query to run faster? Thirdly, a methodological approach may work, if it is based on criteria that really play a role in execution plans. Although I have no personal experience with it, it may be interesting to look into SQL Tuning , by Dan Tow, who bases his methods on relevant single-table and join selectivities.
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Advanced Oracle SQL: Subquery Inline View