> That could work in some cases, however in our case it would
> not produce
> desirable results.
Well I don't think you got Alban's suggestion right...
What he was trying to say was:
- use a regular (not aggregated) function to convert all measures to mm
- use the normal SUM() to sum those value
- use another regular function to convert from mm to whatever
select mm_to_m(sum(convert_to_mm(measure))) from a
Which is easier than my solution.