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Calculate Median in Totals Query

Hi,

This sounds like a fairly hard question which I hope someone can help me on. I have a "Totals" query that groups by certain fields and calculates the Avg. The following is the SQL :

SELECT REGION, INDUSTRY, Avg(MEAN) AS AvgOfMEAN
FROM (tbl1 INNER JOIN tbl2 ON tbl1.DT = tbl2.DT) INNER JOIN tblRt ON tbl1.ID = tblRt.ID
WHERE (((REGION)="North America") AND ((INDUSTRY)="Transportation"))
GROUP BY REGION, INDUSTRY;

Now instead of Avg(Mean) I want the median of the means. How can i do this? Do I need to write a public function and reference it in the query? That I have never done before. Any help is appreciated. Thanks

D

rockiroads

U want a avg of all?

u could try not grouping with the fields
did that work?

SELECT Avg(MEAN) AS AvgOfMEAN
FROM (tbl1 INNER JOIN tbl2 ON tbl1.DT = tbl2.DT) INNER JOIN tblRt ON tbl1.ID = tblRt.ID
WHERE (((REGION)="North America") AND ((INDUSTRY)="Transportation"))

rockiroads

or perhaps

SELECT Avg(AvgOfMEAN)
FROM (SELECT REGION, INDUSTRY, Avg(MEAN) AS AvgOfMEAN
FROM (tbl1 INNER JOIN tbl2 ON tbl1.DT = tbl2.DT) INNER JOIN tblRt ON tbl1.ID = tblRt.ID
WHERE (((REGION)="North America") AND ((INDUSTRY)="Transportation"))
GROUP BY REGION, INDUSTRY) AS qryAvg

lebeau26

ASKER

Sorry, I basically want the Median of the means instead of the Avg of the means. I do want to group by the region and industry though.

So basically it should look like:

Region Industry Median
America Autos 100
England Autos 50
America Food 90
England Food 10

Does this make more sense?
D

Patrick Matthews

Hi lebeau26,

You will need to use a UDF to get a median, unfortunately...

Regards,

Patrick

lebeau26

ASKER

Ok, so how would I do this? Again I have never used a UDF in a query before. I usually just reference them in VBA.

Also, any ideas on how to code the median UDF ?

Thanks
D

Leigh Purvis

Not sure if you'll be able to get a UDF for an aggregate function of course.
But there are many examples of calculating medians out there..
Something like
http://support.microsoft.com/?kbid=210581

Also if on a report - then just this might be useful.
http://support.microsoft.com/?kbid=209244

Lots of different takes on it - like
http://www.aspfaq.com/show.asp?id=2506

And one method from right here that might work for you within a query scenario
https://www.experts-exchange.com/questions/21631892/Getting-Median-value.html

lebeau26

ASKER

"Not sure if you'll be able to get a UDF for an aggregate function of course."

Really? Thats not good because thats what I need. I need it to group by region and then industry and then calculate the median in that.

Is anyone absolutely sure that median can't be done in an aggregate function?

D

ASKER CERTIFIED SOLUTION

Markus Fischer

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Leigh Purvis

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Markus Fischer

This time I should have refreshed. Many things can happen during two phone calls...

I like the SQL solutions in one of Leigh's links, but I'm not quite sure they work in Access as is. Top 1 is not guaranteed to return a single record, which is a problem for subqueries...

(°v°)

Markus Fischer

One more thing:

There are two types of aggregate functions in Access. SQL aggregate functions like Avg(), First(), etc., which cannot be user-defined, and regular VB "domain aggregate" functions like DAvg(), DLookup(), of which you can create new ones.

Note that other major variants of SQL allow the creation of new aggregate functions, but not JetSQL, as far as I know.

If your case, use DMedian( "AvgOfMEAN", "<your query name>" )

(°v°)

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rockiroads

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Jeffrey Coachman

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