真正执行查询，显示查询结果集，显示执行计划，显示统计数据。

Set AUTOTRACE ON: Produces the result set and the explain plan, and lists statistics.

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真正执行查询，但不显示查询结果集，显示执行计划，显示统计数据。

Set AUTOTRACE TRACEONLY: Displays the explain plan and the statistics; you will not see the result set, although the statement is executed.

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优化后的执行计划输出显示出了极大的提高。

The execution plan output after the optimization showed a significant improvement.

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