Next, ensure that the index has these columns in the proper sequence (according to the ORDER BY clause), so that a sort can be avoided.

接下来，确保索引中这些列有适当的顺序(按照ORDER by子句)，这样可以避免排序。

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Therefore, you may often choose to implement indexes that include only the columns referred to in the WHERE and ORDER BY clauses.

因此，您常常可以选择实现只包括在WHERE和ORDER BY子句中引用到的列的索引。

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Like in a regular ORDER BY clause multiple columns can be specified in either ascending or descending sequence.

类似于在常规的ORDER by子句中，可以按升序或降序指定多个列。

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