The min/max cost-based optimization is designed to exploit an existing index to compute efficiently the result of a simple aggregation query involving the MAX or MIN aggregate functions. The goal of this optimization is to be able to compute the result by retrieving only a few rows from the index. To be a candidate for this optimization, the query:
must not contain a GROUP BY clause
must be over a single table
must contain only a single aggregate function (MAX or MIN) in the query's SELECT-list
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