Great QUERY question 2004-03-16 - By Victoria Reznichenko
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"JR Bullington " <bullijr@(protected) > wrote:
> This is for those who love a challenge.
>
> I am trying to come up with a query that would calculate the Standard
> Deviation and Variance for 15 fields. Although in theory this is easily done
> in Access, MySQL does not have the same mathematical calculations that
> Access/SQL does.
>
> Here is the query as it stands in Access:
>
> Select avg(Item01) as Item01a, stdev(Item01) as Item01d, avg(Item02) as
> Item02a, stdev(Item02) as Item02d, avg(Item03) as Item03a, stdev(Item03) as
> Item03d, avg(Item04) as Item04a, stdev(Item04) as Item04d, avg(Item05) as
> Item05a, stdev(Item05) as Item05d, avg(Item06) as Item06a, stdev(Item06) as
> Item06d, avg(Item07) as Item07a, stdev(Item07) as Item07d, avg(Item08) as
> Item08a, stdev(Item08) as Item08d, avg(Item09) as Item09a, stdev(Item09) as
> Item09d, avg(Item10) as Item10a, stdev(Item10) as Item10d, avg(Item11) as
> Item11a, stdev(Item11) as Item11d, avg(Item12) as Item12a, stdev(Item12) as
> Item12d, avg(Item13) as Item13a, stdev(Item13) as Item13d, avg(Item14) as
> Item14a, stdev(Item14) as Item14d, avg(Item15) as Item15a, stdev(Item15) as
> Item15d, avg(overallscore) as overa, stdev(overallscore) as overd from
> tblFacultyEvalSurgery
>
> This is for an online grading system that, except for 5 pages, has been
> converted over to MySQL and Linux / Apache. 2 of which have this problem.
>
> Avg() is easy, but it 's the StDev that I can 't get. St Dev is made from
> Variance (or the mean), which again is not a function of MySQL.
>
> To view the Variance and StDev formulae,
>
http://davidmlane.com/hyperstat/A16252.html.
> If you have any ideas, I will
> be working on this for the next few days.
There are STD()/STDDEV() functions in the MySQL:
http://www.mysql.com/doc/en/GROUP-BY-Functions.html
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