August 2008
Intermediate to advanced
298 pages
9h 22m
English
Content preview from Refactoring SQL ApplicationsBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 5. Statement Refactoring
The problem for us was to move forward to a decisive victory, or our cause was lost.
—Ulysses S. Grant (1822–1885)
Personal Memoirs, Chapter XXXVII
EVEN IF THERE IS OFTEN STILL ROOM FOR IMPROVEMENT WHEN ALL QUERIES HAVE BEEN “TUNED TO death,” as you saw in Chapter 1 (and as I will further demonstrate in the next few chapters), when a big, bad query flagrantly kills performance, improving that query has a tremendous psychological effect. If you want to be viewed with awe, it is usually better to improve a killer query than to humbly ensure that the system will be able to scale up in the next few months.
Although optimizers are supposed to turn a poorly expressed statement into efficient data handling, sometimes things go wrong, even when the indexing is sane and all the relevant information is available to the optimizer. You know how it is: even if the optimizer does a good job 99 times out of 100, it is the botched attempt that everyone will notice. Assuming once again that proper statistics are available to the optimizer, failure to perform well usually results from one of the following:
An optimizer bug (it happens!)
A query that is so complex that the optimizer tried, in the limited time it grants itself, only a small number of rewrites compared to the large number of possible combinations, and failed to find the best path in the process
I’d like to point out that optimizer bugs are most commonly encountered in situations of almost inextricable complexity, ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.