Support distinct

[BohuTANG]

Summary

select count(distinct number) from (select number%3 as number from numbers_mt(100));

[BohuTANG]

@sundy-li

Do we also need to support other distinct?
Such sumDistinct, if need I am happy to open an issue

[sundy-li]

@sundy-li

Do we also need to support other distinct?
Such sumDistinct, if need I am happy to open an issue

Ok, though it's not MySQL style, but it's better than nothing. I'll try to implement a generic combinator for AggregateFunction, such as sumIf, sumDistinct

[BohuTANG]

Sound interesting.
For functions, as long as they are helpful to the user, we should have them(MySQL's style function may not work well for analytics)!
BTW, I have add a functiuon track issue here #758

[BohuTANG]

FYI, all the tracks also in Roadmap: #746