[SQL] Aggregate Functions Template

[Mark Fenbers]

I need to create an aggregate function to do some math not currently 
provided by the available tools.  Can someone point to an example 
aggregate function syntax that I can use as a template for my own 
function.  I'm still a little green on some aspects of PostgreSQL and am 
drawing a blank on how to do this properly from scratch.

Thanks for the help!
Mark
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