I'm wondering if it possible to create a user-defined aggregate that operates on two columns instead of one. Basically, I want to do something like a weighted average where I multiply two columns in each row, sum up the results, and then divide by the sum of one of the fields.

For example, if I had a table that had two columns, call them SuccessRate and TrialSize, and I want to find the WeightedAverageSuccessRate, assuming that the larger the trial size of each data-point, the heavier its success rate would weigh. Hopefully I'm making sense here.

I'd love to just be able to do something like:

SELECT WeightedAVE(SuccessRate, TrialSize) 'WeightedAverageSuccessRate'
FROM MyTable

Although I haven't tried it yet, I'm assuming that this won't work...?

If you have any thoughts, please let me know.

Thanks,
Chris