Standard deviation aggregate function

[kelvincesar]

Hello!

I checked COMPAT.md and didn't find any mention of standard deviation.

Could you confirm if this is correct?
If so, are there any plans to implement it?
I'd be happy to help if needed.

[PThorpe92]

I don't believe that it's planned to go in core directly because it doesn't seem to be built into sqlite (reference), but it would definitely be welcome as an extension.

In fact it could probably just be added to the percentile extension.

[kelvincesar]

Thanks for the response! You're right, it isn't a native implementation for sqlite.

Do you suggest any internal document to read before trying to implement it as an extension?

[PThorpe92]

Yeah the example, is a simple one, but is fairly well documented. The percentile extension already has an aggregate function in there, so it should be pretty simple to follow along :)

Let me know if anything seems un-intuitive or you think needs better documentation, as we're really hoping to make extending functionality as simple as possible