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Comments posted to this topic are about the item Stairway to Data, Step 1: The Basics
Books in Celko Series for MorganKaufmann Publishing Analytics and OLAP in SQL Data and Databases: Concepts in Practice Data, Measurements and Standards in SQL SQL for Smarties SQL Programming Style SQL Puzzles and Answers Thinking in Sets Trees and Hierarchies in SQL




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Nice discussion on the basics...
Where is the information? Lost in the data. Where is the data? Lost in the #@%&! database!  Joe Celko 




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Nice read, puts a lot of good points together very coherently.
Reminded me a lot of a couple of books I use to explain to my wife what I do: The Manga Guides to Statistics and Databases.




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Reminded me a lot of a couple of books I use to explain to my wife what I do: The Manga Guides to Statistics and Databases Ah, the Manga Guide! We all read it; it is good. Well done Joe, it is a great article which I really enjoyed. So many of the subtler problems I have to fix in applications boil down to this sort of problem. There is one chestnut that has always puzzled me. MONEY, like DATETIME, is a quantifier. A MONEY datatype tells you only the amount of money. I'm not a mathematician, but how can division or multiplication be done with a MONEY value as the righthand value (rvalue)? Surely this is a programming error? You can't divide twelve eggs by three eggs can you?
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Phil Factor (5/12/2011)
Reminded me a lot of a couple of books I use to explain to my wife what I do: The Manga Guides to Statistics and Databases You can't divide twelve eggs by three eggs can you?
Don't units of measurement cancel out? 4 feet/2 feet can also be interpreted as "how many times does "2 feet" go into "4 feet" > 2 times. So, wouldn't 12 eggs/3eggs just equal 4?
But, 12/$3 doesn't make sense to me. However, 12 feet/$3 does. (I can, for example, grok "4 feet for a dollar".)
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No problem with every dollar being owned by 4 people.
It's how the fed works, is it not?




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RichB (5/12/2011) No problem with every dollar being owned by 4 people.
It's how the fed works, is it not?
Having worked for the Fed, I took umbrage with that remark  after I finished laughing, of course.
Interesting that you said "every dollar owned by 4 people", as I don't believe that "people" was the specified unit of measure in "12/$3". We use phrases like "4 for a $" all the time, but it only makes sense if the missing unit of measurement can be inferred from the context. E.g. Apples, Feet, Left Nostril Inhalers, etc.
Before I get too far afield, kudos to Joe for an interesting piece. Always good to get something related to databases that isn't just syntax, of config settings, or how to trick SQL Server into doing your bidding.
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Great article  its nice to see someone approaching an understanding of the data that underlies the database!
The discussion about scales that are both nonlinear and directional reminded me of some work I did years ago in economic geography work. Geography is the study of spatial distributions and we were trying to determine from aerial photographs of rural U.S. places where the residents shopped (i.e., which town the farmer/rancher was likely to visit). In the course of our work we came across some earlier research that had used a gravitymodel to determine this  the researchers used an inverse square calculation based on the population (instead of mass) and distance to determine the relative attractiveness of a place. Our photointerpretation work confirmed the model. All we had to do was look at the wear patterns at rural intersections to determine the place to which the residents most frequently traveled. Since then I've been able to use similar models to derived other information from data such as the likelihood of two events being related based on their amplitude/area/concentration and distance apart (on whatever scale makes sense).




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That's right  units cancel when you are dividing, if they are the same. You can't divide a number of eggs by a number of eggs and get a number of eggs. What you get is a pure number (eg. a number of times more fertile chicken A is compared to chicken B, going by the number of eggs laid).
You can divide a number of meters by a number of seconds and get a number of meters per second  a different thing, but quite sensible.
What you can *never* do is add or subtract meters to seconds  or any items which are in different units  and get anything meaningful.
Now, if every column of numeric data on the various DBMSs carried the units around with it (dollars, years, days etc) so that sanity checks of this kind could be performed automatically when queries were created, I wonder how many calculations would get thrown out as total nonsense?




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Nice article, Joe, but I'm a bit dismayed that a putatively authoritative piece on data integrity, organization, and relationships began with a misquoted excerpt of T.S. Eliot's poem.
The quote I find reads:
Where is the wisdom we have lost in knowledge? Where is the knowledge we have lost in information?
(Source: http://www.techsamaritan.org/blog/2010/06/16/chorusesfromtherocktseliot/
I don't mind you paraphrasing, but please indicate that you have done so.
Thanks, Rich



