Computing the Query Ratio
Define the query ratio as follows:
The query ratio is a normalized measure of how much faster a query executes with a join index than without a join index. For example, consulting the table about “Creation and Elapsed Query Times for Different Join Indexes” on page 524, you find a column of calculated query ratios.
You interpret these ratios as follows. Consider the query ratio for the creation cost of a single-table aggregate join index. The reported query value for this join index is 41. This means that the test query runs 41 times faster with the single-table aggregate join index defined than it does without it.