Step 3: Join Selection
The job of the query optimizer is incredibly complex. The optimizer can consider literally thousands of options when determining the optimal execution plan. The statistics are simply one of the tools that the optimizer can use to help in the decision-making process.
In addition to examining the statistics to determine the appropriate use of indexes, the optimizer must consider the optimum order in which to access the tables, the appropriate join algorithms to use, the appropriate sorting algorithms, and many other details that are too many to list here. The goal of the optimizer during join selection is to determine the lowest cost join strategy in terms of logical I/Os and the amount of memory required.
As mentioned at ...
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