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The Art of SQL
Graeme Williams writes "One difference between SQL and a conventional procedural programming language is that for SQL there's a bigger gap between what the code says and what the code does. The Art of SQL is the opposite of a cookbook – or rather it's about cooking rather than recipes. It's not a reference manual, although there's plenty to refer back to. It's an intermediate level book which assumes you know how to read and write SQL, and analyzes what SQL does and how it does it." Read on for Graeme's review.
The Art of SQL
author
Stéphane Faroult with Peter Robson
pages
xvi + 349
publisher
O'Reilly Media
rating
9
reviewer
Graeme Williams
ISBN
0-596-00894-5
summary
An excellent way to improve your approach to SQL
I guess it's normal for an intermediate text to present a number of serious examples, the idea being that the code from an example can be applied to roughly similar problems with roughly similar solutions. I think Faroult's goal is both more abstract and more ambitious. He wants to expand your ability to navigate among and analyze alternative SQL statements with more confidence and over a larger range. This isn't so much a book about SQL as it is about thinking about SQL.
There's almost no chance that the SQL examples in the book will be directly applied to a real problem. The examples are relevant at one remove: What does thinking about this example tell me about thinking about my current problem? So the book doesn't come with downloadable samples. There's no point.
The first few chapters of the book lay a foundation for the rest. As each brick in this foundation is placed, it sometimes feels as though it's placed firmly on your head. Think about indexes ... whack! Think about join conditions ... whack! These chapters have very few examples – the goal is to force you to think through queries from first principles. It's more effective (and less painful) than it sounds.
These introductory chapters cover how a query is constructed and executed, including how a query optimizer uses the information which is available to it. Faroult discusses the costs and benefits of indexes, and the interaction of physical layout with indexes, grouping, row ordering and partitioning. He also explains the difference between a purely relational query and one with non-relational parts, and how such a query can be analyzed in layers. Chapter 4 is available on the book's web page. It will give you a good idea of the style of the book, but not of the level of SQL discussed – the longest example in the chapter is just 15 lines.
Chapter 6 presents and analyzes nine SQL patterns, from small result sets taken from a few tables, to large result sets taken from many tables. The chapter falls roughly in the middle of the book, and feels like its heart. Prior chapters have built up to this one, and subsequent chapters are elaborations on particular topics. The theme of the book, to the extent that it has one, is that details matter. Different SQL statements can be used to produce the same result, but their performance will be different depending on details of the data and database. A change to the database structure, such as adding an index, might improve performance in one set of circumstances, but make it worse in another. The case analysis in this chapter will make you more sensitive to details in query design and execution.
The authors almost never mention particular database products. Their justification is that any absolute statement would be invalidated by the next release, or even a different hardware configuration, and anyway, that's not the business they're in. But sometimes this can go too far. The phrase "A clever optimizer ... will be able to" is too hypothetical by half. Is this an existing hypothetical query optimizer, or a vision of a future optimizer? Or the optimizer of one hypothetical database product and not of another? I suspect that Faroult knows and is simply being coy. It's just unhelpful not to tell us what existing databases will do, even if depends on the release or the hardware.
Faroult does this because he's not much interested in telling you what actually happens when a particular SQL statement is executed by a particular database. If the authors wanted a cute title for the book, I'm surprised they passed over The Zen of SQL Maintenance. When you look at an SQL statement, Faroult wants you to see what other SQL statements would do under other circumstances. He literally wants you to see the possibilities.
The second half of the book continues the analysis of chapter 6 into special cases, such as OLAP and large volumes of data, monitoring and resolving performance issues, and debugging problematic SQL.
Chapter 7 discusses tree-structured data, like an employee table with a column for the employee's manager. Faroult likes his own solution best, but presents an alternative approach by Joe Celko clearly enough for you to explore that as well.
Chapter 8 includes a series of examples of SQL and PHP. For anyone like me who spends more time in various programming languages than in SQL, this chapter is a small gem. It nicely illuminates the care needed in deciding what happens in code and what happens in SQL.
Chapter 9 addresses locking and concurrency, as it applies to both physical and logical parallelism. Transactions are included, but the discussion is just one part of a 20-page chapter and seems thin.
The Art of SQL is very clearly written. Whether it is "easy" will depend on how comfortable you are with SQL. This book is targeted at (page xi) "developers with significant (one year or, preferably, more) experience of development with an SQL database", their managers and software architects. I have months of experience spread over a decade or more, so I'm nominally outside the target audience. I found the SQL examples and discussion clear once I had a chance to let them sink in. If you're working with SQL regularly, they'll be perfectly clear.
The graphs let down the otherwise high quality of the book. For example, Figure 5-3 shows a rate (higher is better) but the legend says "Relative cost" (higher is worse). Figures 9-1 through 9-3 on facing pages 228 and 229 show response time histograms for three different query rates but don't show what the rates are. The x-axis of Figure 10-1 seems to be calendar time, but it's decorated with a stop watch icon. And as a representative of rapidly aging boomers with rapidly deteriorating eyesight, could I beg book designers not to put figure legends in a smaller font than the text of the book? Diagrams should be simple and clear, not something to puzzle over.
This is a book to conjure with, but it's not a book for everyone. Some people may find it too abstract, with too much discussion of too few examples. If you're completely new to SQL, the book will be hard going. If you have very many years of experience with SQL, it's just possible that you won't find anything new in the book, although I expect you'll find a lot to think about. For anyone in between, The Art of SQL is a excellent way to improve the way you attack problems in database and query design.
You can purchase The Art of SQL from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
I guess it's normal for an intermediate text to present a number of serious examples, the idea being that the code from an example can be applied to roughly similar problems with roughly similar solutions. I think Faroult's goal is both more abstract and more ambitious. He wants to expand your ability to navigate among and analyze alternative SQL statements with more confidence and over a larger range. This isn't so much a book about SQL as it is about thinking about SQL.
There's almost no chance that the SQL examples in the book will be directly applied to a real problem. The examples are relevant at one remove: What does thinking about this example tell me about thinking about my current problem? So the book doesn't come with downloadable samples. There's no point.
The first few chapters of the book lay a foundation for the rest. As each brick in this foundation is placed, it sometimes feels as though it's placed firmly on your head. Think about indexes ... whack! Think about join conditions ... whack! These chapters have very few examples – the goal is to force you to think through queries from first principles. It's more effective (and less painful) than it sounds.
These introductory chapters cover how a query is constructed and executed, including how a query optimizer uses the information which is available to it. Faroult discusses the costs and benefits of indexes, and the interaction of physical layout with indexes, grouping, row ordering and partitioning. He also explains the difference between a purely relational query and one with non-relational parts, and how such a query can be analyzed in layers. Chapter 4 is available on the book's web page. It will give you a good idea of the style of the book, but not of the level of SQL discussed – the longest example in the chapter is just 15 lines.
Chapter 6 presents and analyzes nine SQL patterns, from small result sets taken from a few tables, to large result sets taken from many tables. The chapter falls roughly in the middle of the book, and feels like its heart. Prior chapters have built up to this one, and subsequent chapters are elaborations on particular topics. The theme of the book, to the extent that it has one, is that details matter. Different SQL statements can be used to produce the same result, but their performance will be different depending on details of the data and database. A change to the database structure, such as adding an index, might improve performance in one set of circumstances, but make it worse in another. The case analysis in this chapter will make you more sensitive to details in query design and execution.
The authors almost never mention particular database products. Their justification is that any absolute statement would be invalidated by the next release, or even a different hardware configuration, and anyway, that's not the business they're in. But sometimes this can go too far. The phrase "A clever optimizer ... will be able to" is too hypothetical by half. Is this an existing hypothetical query optimizer, or a vision of a future optimizer? Or the optimizer of one hypothetical database product and not of another? I suspect that Faroult knows and is simply being coy. It's just unhelpful not to tell us what existing databases will do, even if depends on the release or the hardware.
Faroult does this because he's not much interested in telling you what actually happens when a particular SQL statement is executed by a particular database. If the authors wanted a cute title for the book, I'm surprised they passed over The Zen of SQL Maintenance. When you look at an SQL statement, Faroult wants you to see what other SQL statements would do under other circumstances. He literally wants you to see the possibilities.
The second half of the book continues the analysis of chapter 6 into special cases, such as OLAP and large volumes of data, monitoring and resolving performance issues, and debugging problematic SQL.
Chapter 7 discusses tree-structured data, like an employee table with a column for the employee's manager. Faroult likes his own solution best, but presents an alternative approach by Joe Celko clearly enough for you to explore that as well.
Chapter 8 includes a series of examples of SQL and PHP. For anyone like me who spends more time in various programming languages than in SQL, this chapter is a small gem. It nicely illuminates the care needed in deciding what happens in code and what happens in SQL.
Chapter 9 addresses locking and concurrency, as it applies to both physical and logical parallelism. Transactions are included, but the discussion is just one part of a 20-page chapter and seems thin.
The Art of SQL is very clearly written. Whether it is "easy" will depend on how comfortable you are with SQL. This book is targeted at (page xi) "developers with significant (one year or, preferably, more) experience of development with an SQL database", their managers and software architects. I have months of experience spread over a decade or more, so I'm nominally outside the target audience. I found the SQL examples and discussion clear once I had a chance to let them sink in. If you're working with SQL regularly, they'll be perfectly clear.
The graphs let down the otherwise high quality of the book. For example, Figure 5-3 shows a rate (higher is better) but the legend says "Relative cost" (higher is worse). Figures 9-1 through 9-3 on facing pages 228 and 229 show response time histograms for three different query rates but don't show what the rates are. The x-axis of Figure 10-1 seems to be calendar time, but it's decorated with a stop watch icon. And as a representative of rapidly aging boomers with rapidly deteriorating eyesight, could I beg book designers not to put figure legends in a smaller font than the text of the book? Diagrams should be simple and clear, not something to puzzle over.
This is a book to conjure with, but it's not a book for everyone. Some people may find it too abstract, with too much discussion of too few examples. If you're completely new to SQL, the book will be hard going. If you have very many years of experience with SQL, it's just possible that you won't find anything new in the book, although I expect you'll find a lot to think about. For anyone in between, The Art of SQL is a excellent way to improve the way you attack problems in database and query design.
You can purchase The Art of SQL from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
... the reviewer has abolutely no idea what he just read?
I know Amazon has software patents and all, but this (and just about every other book I see reviewed here) is ~20% cheaper at Amazon than it is at BN...
SQL is implemented differently in all of the environments I have encountered it (yeah, I'm not a PRO, just a hacker, so don't hate on me.) Those environments are MS SQL, MySQL, FoxPro, and MS Access. I think I messed around with PostgreSQL. Maybe a few others.
Point is nothing is really transferable and even basic syntax varies widely as do optimizations and 'the best way to do x'.
It's great to see a book that tells me SQL can do pretty much anything - but I pretty much already knew that.
This book might be good for THEORY, but for actually getting useful and applicable information, the review leaves me wondering who would be a worthwhile reader.
If you think SQL is an "art," you are a hack. Designing proper databases and the SQL to use them optimally falls under the domain of science/engineering. 95% of developers see relational databases simply as a means for a persistent data store, but that's not what it was designed to do. If you don't know engineering (what you do when designing functional systems*) from art (painting pictures, etc) you should have gone to a better college.
See this page for a start on the science of databases.
*Yes, I know creativity is usually involved when designing things. That doesn't make it art.
A slashdotter who didn't build his own computer is like a Jedi who didn't build his own lightsaber.
"for SQL there's a bigger gap between what the code says and what the code does"
I couldn't agree more. Sometimes while working in SQL I really wish I had a time machine and a rubber hose.
Book reviews seem so out of touch with the flow of the rest of Slashdot (except to the extent that everyone can comment about stuff they haven't read).
Could Slashdot not post book reviews to the main section?? At least not at the same level as a news story that locks Slashdot for an hour - maybe just a sentence "Art of SQL review" with a link then post a real news story as well.
The reviews are neither timely news nor really commentable (although that rarely stops us).
I quite like having the section and appreciate the time the authors put into these reviews (and have bought a couple because of that), but they shouldn't be mixed into the news postings.
Ya, its off topic, but you are right. This new slashdot is nice and all, but stuff needs to go where it belongs.
Click Click Bloody Click PANCAKES!
Chapter 7 discusses tree-structured data
Looks like no discussion of many-to-many relationships. This would make any book on databases and sql queries of limited value, not much more than a beginner book.
Trees are of limited value, they only exist in special circumstances. If you stick to tree structured data relations then you will almost always have to do wierd hacks that may threaten data integrity.
While many-to-many *seems* harder, as a data model M:M is often a much better practicle solution. As well as modeling the reality of the situation in a much more accurrate manner.
My $.02
putting the 'B' in LGBTQ+
I can't mod you up because I don't have any mod points, but I agree that I preferred the old one.
To keep this at least somewhat on topic, the table with the book information seems to have 0 margins/padding, making it a little ugly/difficult to read.
Perhaps that's what's wrong with database development these days (just check out The Daily WTF, as it seems they have a SQL example every other day). When a single year of experience is considered "significant" and "experienced", it's no wonder there are so many crap DBAs out there. We look for people with 5+ years of C# experience (ha! Good luck finding someone with more than 5 years experience ...) for intermediate-level developer positions. There's no way someone with only a year of SQL experience would qualify for an intermediate-level DBA position.
Just as background, I've been doing development on SQL Server for 6 years now (from SQL 7 to SQL 2005). I'm still learning, still finding ways to improve my code's cleanliness and performance, still finding new things I can do in SQL. For example, SQL 2005 finally has CTEs, making it only the second database to implement that ANSI SQL99 standard. CTEs make it very easy to do things that were painfully hard before, like walking a tree or implementing a recursive algorithm over sets of data.
After my fourth year of working with SQL, I'd have been willing to say I had "significant" experience with SQL. Four years is arbitrary -- it really depends on how much you work with it day to day. Someone may have "significant" experience after only two years, while someone else may not be significantly experienced until he's worked with SQL for eight years. If you had to put a number of years on what would constitute significant experience, I'd err on the safe side and go with three or four years. Certainly not just one year.
I spend much of my time explaining why a 5 page SQL statement "that takes a long time" is NOT A DATABASE PROBLEM!
/rant
One difference between SQL and a conventional procedural programming language is that for SQL there's a bigger gap between what the code says and what the code does.
That's kinda the point. Since data management is based on a complete theory, it's possible to write what you want *declaratively*, and let the DBMS figure out how to do it. You might be familiar with another declarative mini-language: arithmetic. For example, you write "1+2*foo", knowing that the computer will figure out how to compute that and (conceptually) replace it with a result value. SQL should be the same way (but of course they fucked it up and ends up being half-procedural, half-algebraic, guaranteeing that both the people who understand databases and the people who don't will be equally confused).
The first few chapters of the book lay a foundation for the rest.
Get a book on relational theory (I recommend Database In Depth, only 250 pages). Then you will have a *real* foundation.
The phrase "A clever optimizer ... will be able to" is too hypothetical by half. Is this an existing hypothetical query optimizer, or a vision of a future optimizer?
There's no "existing hypothetical" query optimizer. That doesn't even make sense. But the point is, this shouldn't be the first concern when formulating database queries. In theory, you should be able to write any equivalent query and have it run at the same speed, so start with that in mind and then optimize when needed.
because he's not much interested in telling you what actually happens when a particular SQL statement is executed by a particular database
No shit, if you're trying to understand data management, don't waste time thinking about PRODUCTS. Products come and go, data management theory won't change unless the universe does. Would you expect a book on calculus to talk about which form of integral is faster to computer? That comes AFTER you master the fundamentals.
Start with a good book on theory, figure out how to translate simple, concise relational algebra queries into SQL (and wince), then figure out how to make them go faster. As an added bonus, you'll also understand object (network) and XML (hierarchical) models (such as they are), since they are just subsets of the relational model.
Many so-called book reviews on Slashdot fail to review the book. Instead, they simply state what each chapter covers. This review is actually useful. It describes the book's target audience, gives a sense of what the book does and doesn't contain, and helps me understand whether the book would be useful to me. Thanks!
there's a bigger gap between what the code says and what the code does
That's stated incorrectly. With SQL, the code says what to do, but it does not say how to do it. That's the difference between "normal" procedural code and languages like SQL.
Software sucks. Open Source sucks less.
Ahhh - but the best scientists are artists as well. (In fact, scientists and mathematicians often have more in common with artists than engineers).
Sure, the mechanics of programming is rather dull and boring, but large scale system design often requires considerable creativity that is much better done by people not constrained by artificially perceived IT limitations.
Coding J2EE isn't an art, but designing/building a massive neural net or complex, distributed game/simulation is. MySpace, Google, eBay, etc weren't concieved by 'classic' engineers, but, rather, by creative people who understood how technology can enable new paradigms.
Pretty much every book on SQL I've seen only gives you obvious examples and covers the most simple uses. Every project I've worked on (for about 10 years) where there is pre-existing SQL written, almost all of it is written inefficiently. I'm not sure this book explains this kind of thing. But I've found 99%+ of the time you don't need to use a cursor, and it's almost always slower.
SQL can do a lot more than most programmers ever try to do with it. There are a lot of clever tricks you can use exploiting its set based nature. The only place I've seen clever solutions beyond simple insert/delete/update statements is some of the trade magazines; the one for MS SQL Server sometimes has some very neat examples. These trade magazines have examples and ideas presented using the SQL language of a particular database, but it's almost always portable wihtout much work. I consider myself pretty good at SQL and even I find it's hard to learn more to get to the point where I can design clever SQL more frequently. Anyone else find that too?
Another thing I've noticed is on some open source projects (and perhaps some closed source ones), particularly web based ones, there is displayed at the bottom the number of database queries used to generate the page. They are often 10 or more, which almost always seems ridiculous. I think there just aren't all that many people out there who understands what SQL can do, how it's different than procedural languages and how to use it beyond a simplistic straight forward approach. Hopefully this book helps explain that - I'll probably browse a bit the next time I'm in a book store.
One difference between SQL and a conventional procedural programming language is that for SQL there's a bigger gap between what the code says and what the code does.
What? My SQL code tends to do exactly what the code says it will, are you trying to say that it's a high level language or am I missing something here?
... trying to read the sample chapter screws up the tab holding that page in firefox (1.5.0.4) - scrolling no longer works for that tab until you either close it or go to another url, etc. It's too bad, it sounds like a good read.
And yet, if you get out and talk to some of the real-world database consultants who get called in to clean up other people's messes, one of the complaints you hear again and again is that too many so-called DBAs learned their trade on a specific product, rather than understanding why databases work the way they do.
Optimizations that you introduce into your applications to cater to specific products' features (or work around their shortcomings) may be a fact of life, but they make for poor design choices. You should know what you're doing first -- which means a good understanding of database theory -- and layer all that syntactic hot-rod stuff on later.
Breakfast served all day!
I'm slowly working my way through it; it's a great book on a number of levels. The writing itself is very nice, with a real personality showing through and not just the usual dry technical flavor. The illustrations are done in a nifty "drawing" style that looks good and portrays the data well. The technical insights are very helpful; after reading what I've moved through so far I've rewritten some of my Rails code to be more efficient.
I highly recommend this book; the $40 you'll spend on it will be repaid the first time you delete a swath of Java looping code and replace it with an additional subquery. If I can do half as well on my next book I'll consider it a job well done.
The Army reading list
bookpool has it cheaper than amazon.
It's hard to believe that's how Micronians are made. Why don't we see it right now by having you both kiss one another?
+---------+
| You |
+---------+
| Fail It |
+---------+
1 row in set (0.08 sec)
damn... I always read GOLD when I have no mod points... mod parent up!!! Funny++
I have found (and who can disagree (just trolling)) that at least half of the production databases that I have come across hare not normalized. Go figgure.
Anyway, this being the case, I have found that SQL is poor in handling a non-normalized table/database. (cant really call a non-normalized table as a database can we? (nuther troll))
For example. We keep a complete record for each person for each pay period. Even inactives.
I am asked to give a list of all active employees for a date range, and a lot of payroll detail, personal detail, etc. Guess what? Simple SQL gives a lot of duplicate names. I wish that there was a simple way filter. (Yes, I can do this in sql, but my point is that it is not handled natively in sql. I would like a simple command - give me all names and all their data for the latest pay period - something like that.
All procedural languages will handle this problem nicely.
metaphors be with you
Not every programmer needs to be a computer scientist, but they do need to learn a little theory now and then. That's especially true when you're work with relational databases, which are full of weird abstractions and subtle performance issues. Not having looked at this particular book, I can't say whether its overkill for what most SQL people do. I can say that most database hackers don't seem to know as much theory as they should.
Wouldn't that rather be "SELECT TOP 1 FROM Posts WHERE sid=#06/06/07/194246#" ?
I think we can keep recursing like this until someone returns 1
You can get "Art of SQL" cheapest at Buy.com, see:
Lowest Prices for 'Art of SQL'
hmmmm...let's test that:
SELECT Creativity.Passion, Creativity.Insightfulness, Ability.Palette, Ability.Colorscheme FROM Creativity INNER JOIN Ability ON Creativity.AbilityID = Ability.AbilityID WHERE Creativity.Passion = "Mediocre";
Result Set:
Creativity.Passion | Creativity.Insightfulness | Ability.Palette | Ability.Colorscheme
Mediocre | Dreamer | Basic | Shit Brown
I have way too much time on my hands.
In fact, if you have access to a local, independently-owned bookseller in your area, you should be buying your books there instead of online.
Stacey's Books in San Francisco doesn't give me Amazon's 34 percent discount -- in fact, it gives me 10 percent -- but it is a wonderful resource and not one I'd like to see disappear.
That's not hyperbole either. This year we've seen two classic, quality Bay Area bookstores close their doors: Cody's on Telegraph Avenue in Berkeley and A Clean, Well-Lighted Place for Books on Van Ness in San Francisco. These were not holes in the wall; they were spacious, carried a lot of stock and had served their communities well for years. (And believe me, the Bay Area in general buys a lot of books.)
The reality is that the book market is changing. Superstores like Borders and Barnes and Noble have a lot to do with it, and so does Amazon. Another factor is the overall decline in book sales to the American public. People walk into Borders to buy DVDs of Friends and they pick up a paperback of Harry Potter at the same time. That's not the model I want my booksellers to be based around; I want to support local businesses that understand their communities and are dedicated to selling books.
This is not to knock Amazon, or Borders or B&N for that matter; in communities where those are the only option, it's better to have someplace to buy books than no place at all. I still buy plenty of stuff at Amazon. But for books, I vote with my wallet.
Breakfast served all day!
"One difference between SQL and a conventional procedural programming language is that for SQL there's a bigger gap between what the code says and what the code does."
Well, certainly one difference between SQL and a conventional procedural programming language is that SQL isn't procedural, it's declarative. One describes the data a query such produce, rather than state a set of steps necessary to achieve a desired result.
jbgreer
The Norton Anthology of English Literature, 4th Ed., Vol 2
The reviewer managed to miss something that's pretty important: the authors are totally infatuated with Sun Tzu's The Art of War, even to the point of copying that book's chapter titles. Which is evidence either that they're educated people building on age-old wisdom — or they're half-educated dweebs copying a book that's faddish right now.
One difference between SQL and a conventional procedural programming language is that for SQL there's a bigger gap between what the code says and what the code does
Or more importantly SQL is not a procedural programming language at all. Please don't try to compare the two together at all, it just leads to misconceptions about what SQL is and how it works.
I like the look of this book quite a bit, judging soley from the sample chapter. It talks in a straight-forward manner about the factors that determine how a database goes about it's job and how you can make that job easier or harder. If the rest of the book plays out similarly then thorough understanding of this book as well as Tom Kyte's would make for a programmer I'd love to hire.
References to Knuth's volumes titled "The Art of Computer Programming" http://www-cs-faculty.stanford.edu/~uno/taocp.html
are sprinkled liberally throughout many, many papers in computer science, especially wrt algorithms. It's more of an abstract art, as opposed to the "physical" arts like paintings and sculptures. You can't ignore the engineering aspect of it, yes, but if you manage to engineer a system well AND do so with simplicity, elegence, and creativity ... well, that distinguishes the true progessional.
You'd think that they'd have tested that sort of thing.
Especially when it would have only taken one or two people a couple of work days at most to really go over it all and make sure that there were no glaring errors in the layout.
Working at Slashdot must be the most relazing experience in the world, what with all that not working that they do.
EVERYTHING is transferable. That is, everything you've actually learned, everything you understand. If you're just mashing buttons, yeah, you might be a little lost when the buttons change. When telephones changed from rotary dial to push buttons, some people were still able to make calls. If course the basic syntax changed, and knuckle-draggers like the folks who modded the parent comment Insightful were SOL. But most folks who had some ideas about the THEORY of the telephone--that the little spinning disk on the phone didn't make the actual call but rather transferred information, and the buttons were just a new way of transferring the same information--adapted and moved on.
The fact that a computer even let such a concept be typed and communicated gives me hope for the day when machines rule the Earth, that they just might have enough of a sense of humor, or pity, to allow us humans to remain in their midst.
I have to recommend a good under $20.us book to go with it.
http://www.powells.com/biblio?isbn=0071359532
Having to work for a living is the root of all evil.
Bills of Materials lend themselves perfectly well to tree structures.
You better watch out, there may be dogs about . .
According to Aristotle, arts have techniques, while sciences have laws.
Actually, they don't, in the sense that there is no one single built-in command to handle this case. Just like in SQL, you (or someone else) has to write the function that performs a 'select distinct' equivalent.
Unless you're using a targeted-product (one built specifically for your data needs), nothing you do will be handled natively in any language. You can build this functionality by using correct SQL or writing the appropriate functions in a procedural language.
And why don't you consider 'select distinct' a built-in function?
Storing things as adjacency lists (which, obviously, is an M2M table where the node properties live in their own normalized table) tends to be faster in the long run for all but the largest and most active trees.
;-)
Nested sets are cool, and I've implemented them (in MySQL 4.1 no less), but at the end of the day, traversing a graph happens far more often and more usefully.
This seems to be where the CS majors separate from the rest of the crowd. Point out that they ought to know how to do this unless they failed 2nd year
Remember that what's inside of you doesn't matter because nobody can see it.
the old HTML was much much better.
The HTML hasn't changed at all. It's the CSS that's changed.
Are we talking parent-child hierarchy tables? If so, Oracle's had statements to take care of that for a long time, since 1998 or so. Perhaps not ANSI standard, but they get the job done.
You better watch out, there may be dogs about . .
If you are going to go with the cooking/food reference then I do not think SQL is like cooking. SQL is like ordering at a restuarant, where the restuarant is your DBMS. It's like programming in prolog. You don't tell prolog what to do; you tell it what you want. Just a thought.
you.
Save yourself $7.65 by buying the book here: The Art of SQL. And if you use the "secret" A9.com discount, you can save an extra 1.57%!
Regarding > "there's a bigger gap between what the code says and what the code does." I think that's a typo. It should read...
there's bigger CRAP between what the code says and what the code does.
There's a lot of code in the RDBMS and normally you shouldn't have to delve into the RDBMS' source... But you should know what it does and how to use it.
I was once on a project where a DUHveloper needed to perform an unnatural sort on a key column. He needed to display the query results where certain rows always needed to be sorted to the end of the result set but there were no column values to meet the criteria. He had this HUGE amount of nested if statements that he had been working on for days. After I inquired as to what he was wasting all of his time on I showed him how to create a sort non-displayed column where you derive a value based on a CASE statement. I accomplished in 5 minutes what he had struggled for days on just because he didn't really know much about SQL.
I've corresponed with Mr. Faroult on several occasions, I've used many of his scripts, and I've received a lot of email help from him... So based on my experience I'm betting his book is pretty good.
Can I pick the old CSS style?
... cover JoSQL (http://josql.sourceforge.net), in fact it's single focus on RDBMS's is a shame, since SQL is used in many places other than RDBMS's.
You want to get theorrectical, here it is:
SQL is declartive - the user simply "declares" what s/he wants. It's up to DBMS/DBA to figure out how to execute the tasks. If the result is too slow, IT IS DBA (and DBMS) PROBLEM.
So it's like Alton Brown's "I'm Just Here for the Data"?
Yeah, I can understand the nostalgia for a bookseller who "knows what I want" and "understands the community". But, reality check, Amazon recommendations churned out from a little AI magic and some freakishly large database just utterly destroy anything a minimum-wage retail staffer with no knowledge of my tastes can hope to accomplish. "Well what do you like?" "Hmm, I don't know, a bit of everything. I read a lot of fantasy or Tom Clancy.". "Well, in that case, can I recommend you go to our fantasy or Tom Clancy shelves?" (Gee thanks, why didn't I think of that.) Amazon *knows* that there is a British alternate history of the Napoleonic Wars fought with dragons that is right up my alley (incidentally: it starts with His Majesty's Dragon, and I'm *loving* it).
Community involvement... well... I'm all for teaching kids to read and exposing them to the classics. And I support libraries, churches, and schools that do. But bookstores are, well, poorly suited to the task. I also, how do I put this gently, sort of fail to be a member of the community the bookstore is representing on a regular basis? I live in Japan at the moment -- the most community-oriented mom&pop bookstore around here can't possibly be community-oriented and still be Patio11-oriented. If I got a job in San Fransisco, I'd be pretty bloody out of place as the Catholic Republican and some of my reading selections might not make a San Fransisco bookseller abundantly happy. Then there's just the practical limits of bookseller expertise and shelf-space: excuse me, Mr. Mom&Pop Bookseller, can you recommend me a good book for a twenty-something set in modern China written in English which is *nothing like* Shanghai Baby? Thats what I was looking for the last time I bought a birthday gift from Amazon, and you can browse yourself a dozen choices in less time than it takes to get to the head of the line to speak to the clerk.
Help poke pirates in the eyepatch, arr.
It is hard to know what is the right thing to do. Although, I want to support my local stores and community, I also don't want to use up trees. So is buying online and reading online better than buying a mass published book from a local store?
You can tell the DBMS HOW to do it, IF you write your queries correctly.
Too many people write their queries 'top down'. In order to specify how the query will execute you need to right your queries 'right to left'.
WTF? Attend:
SELECT *
FROM TableA
INNER JOIN TableB
ON TableA.PK = TableB.FK
WHERE TableA.Field1 = "A"
AND TableB.Field2 = "B"
as opposed to
SELECT *
FROM (SELECT * FROM TableA WHERE Field1 = "A") AS A
INNER JOIN (SELECT * FROM TableB WHERE Field2 = "B") AS B
ON A.PK = B.FK
This, in effect, ENSURES that the 'WHERE' clauses will be executed first, and the join operation will be performed on minimal sets (post filtering).
NB: Filtering is faster than joining, do the filtering first.
"umm... dude? SQL has been around since the mid 50's." ?
:-)
:-)
Why did the parent post rate informative?
"A guy at ibm," you say
The theory came out in 1970, so you're off by 15 years.
Off 20 years for an actual implementation (mid 70's).
Off 25 years for commercial product (79).
http://en.wikipedia.org/wiki/SQL#History
----
"anchronistic and irreperably flawed." ?
"Duuuude!"
What would you replace it with?
By ANY measure, relational databases are a RESOUNDING
success. They're as much a part of the computer world
as operating systems, networking, and compilers.
...The Art of SQL Injection. tough choice.
If you think
will get a sequel
Wouldn't it be nice if you could choose which CSS style you wanted in your preferences.
... 95% of developers see relational databases simply as a means for a persistent data store, but that's not what it was designed to do.
This developer doesn't. I prefer flat files, especially for storing large amounts of raw binary data.
But nearly every time I have a review for a design that uses flat files for persistent storage, the DB wonks have conniption fits and insist that I use a DB.
I think it's the DB enthusiasts that have the problem.
In the course of every project, it will become necessary to shoot the scientists and begin production.
You have it backwards. Traversing a graph is an iterative operation. RDBMSs are designed for set operations. Nested sets are much faster for reading than an adjacency list but are also much slower for updating. In a large, highly active tree, nested sets may not meet performance constraints.
.5 seconds for any node in the database. Selecting the descendants iteratively is faster only in the special case of few descendants and takes anywhere from .25 seconds to 20 seconds.
To put things in perspective, I have a nested set tree with a ragged hierarchy with 50k nodes. Node level security is in place. A worst case insert currently requires 1.5 seconds. Selecting the descendants of a node and filtering against the ACLs requires
The tree is read more often than it is updated so the nested set meets my performance goals in all current cases while adjacency lists do not meet my goals in some cases.