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Stairway to Data, Step 1: The Basics Expand / Collapse
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Posted Wednesday, May 11, 2011 10:45 PM


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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 Morgan-Kaufmann 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
Post #1107465
Posted Thursday, May 12, 2011 1:00 AM
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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 --




Post #1107494
Posted Thursday, May 12, 2011 3:55 AM
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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.



Post #1107554
Posted Thursday, May 12, 2011 4:16 AM


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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 right-hand value (rvalue)? Surely this is a programming error? You can't divide twelve eggs by three eggs can you?



Best wishes,

Phil Factor
Simple Talk
Post #1107569
Posted Thursday, May 12, 2011 6:32 AM


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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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Post #1107639
Posted Thursday, May 12, 2011 6:45 AM
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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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Posted Thursday, May 12, 2011 6:57 AM


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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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Post #1107656
Posted Thursday, May 12, 2011 7:00 AM
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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 gravity-model 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 photo-interpretation 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).
Post #1107660
Posted Thursday, May 12, 2011 7:13 AM
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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?
Post #1107678
Posted Thursday, May 12, 2011 7:58 AM


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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 mis-quoted 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.tech-samaritan.org/blog/2010/06/16/choruses-from-the-rock-t-s-eliot/

I don't mind you paraphrasing, but please indicate that you have done so.

Thanks,
Rich
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