In my previous blog, I discussed the approximate count of unique values for which a predefined function is available in Impala (NDV), Oracle 12c (APPROX_COUNT_DISTINCT) and in MongoDB (estimatedDocumentCount()).
However, I didn’t mention about SQL Server since there is no such function available in the versions I am using. However, the function has been introduced in SQL Server 2019.
The function Approx_Count_Distinct does the same thing as mentioned in my previous blog.
If you want to know more about this function, I would suggest you click here. This guy (Rajendra Gupta) didn’t leave any opportunity to discuss this functionality as he concentrated on each piece and clarified each and every point.
Big Data and SQL 