Aram Fingal <fin...@multifactorial.com> writes:
> Suppose I'm doing a group by query like the following:
> SELECT drug1, drug2, AVG(response)
> FROM data
> GROUP BY drug1, drug2

> The problem is that the same drug may appear sometimes as drug1 and sometimes 
> as drug2.  So, for example, the combination "aspirin, acetaminophen" may also 
> appear as "acetaminophen, aspirin" and I want these grouped together in the 
> query.  Is there a simple way to do this?

Easy way is something like

SELECT LEAST(drug1, drug2), GREATEST(drug1, drug2), AVG(response)
FROM data
GROUP BY 1, 2

though it'd be a PITA to scale that to more than 2 drugs.

                        regards, tom lane

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