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voyager838
Yak Posting Veteran
90 Posts |
 Posted - 2010-11-05 : 09:44:18
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| Hi!Wonder if someone knows how to calculate histogram in sql query?I know how to do it mathematicly but not in a single query.Can it been done ?Any tips/ideasThanksV |
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shebert
Yak Posting Veteran
85 Posts |
Posted - 2010-11-05 : 10:50:23
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| How do you do it mathmaticaly? |
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voyager838
Yak Posting Veteran
90 Posts |
Posted - 2010-11-06 : 17:45:19
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quote:
Originally posted by shebert
How do you do it mathmaticaly?
Hi Sherbert!Sorry not to answer so quickly on your good questions.Unfortunate i will have to jump over to answer all the details how to do it mathematics for the moment, and show how i have "been" solve it. Its not particular dynamicHere is the base:Lets say you have an table T with values where the min-value is 0 and max-value that is 25. And we want it now to be classified in 5 bars, The interval would be:I = (25 - 0) / 5 = 5Formula:(max_value - min_value) / number_of_barsThan we could write something like select count(A) AS Bar_0_5 from T where A >= 0 AND A < 5union select count(A) AS Bar_5_15 from T where A >= 5 AND A < 10unionselect count(A) AS Bar_10_15 from T where A >= 10 AND A < 15union select count(A) AS Bar_15_20 from T where A >= 15 AND A < 20unionselect count(A) AS Bar_20_25 from T where A >= 20 AND A <= 25note: the interval here has 5 steps on each bar.It counts every single value from that table T where in the field A has an certain value that close up to an certain bars.very simple.Now, the though here is to do it more dynamic, so it can be reusable.That is the problem.Hope someone could figured out, if it can been done.I have an suggestion for an solutions, but it doesn't really looks good. thxV |
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Histogram