APPROX_COUNT_DISTINCT( expression ) evaluates an expression for each row in a group, and returns the approximate number of unique non-null values in a group. This function is designed to provide ...

Yet another excellent paper on optimising distinct count measures from the SQLCat team: Actually I’m beginning to wonder whether I should be linking to the SQLCat team site – in the sam… ...

Great blog entry from Denny Lee on optmising distinct count measures here: I’d seen a ppt deck of a presentation he did at PASS a few years ago where he first set out these ideas, but it lo… ...

We consider a new type of distinct element counting problem in dynamic data streams, where (1) insertions and deletions of an element can appear not only in the same data stream but also in two or ...