In this blog post series, we are looking at noteworthy enhancements to the Oracle Multitenant option of the Oracle Database in 12.1.0.2. In the previous post, we looked at the new Attribute Clustering feature, which along with the Zone Maps feature, can help in I/O pruning of data. Now we look at a new SQL function. APPROX_COUNT_DISTINCT() is a brand new SQL function in Oracle Database 12.1.0.2 that allows approximate count distinct, instead of exact. This allows counting of distinct values to be much faster for voluminous data, and when there are many distinct values. The value returned is negligibly different to the exact distinct count. Large-scale data analytics often requires the repeated counting of distinct values, however this type of analysis is normally fine with approximate almost exact results. In such a case, using the new APPROX_COUNT_DISTINCT() function with the ability to decrease the processing time is very useful. Resource consumption is also reduced. The syntax is as follows: select approx_count_distinct( ) as " " from ; For more on this function, please refer to the SQL Language reference here . In this series, we have gone through the enhancements to multitenant in Oracle Database 12.1.0.2. For reference, a full list of the enhancements is available in the documentation here .
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