If all the columns in the clause appear in the required sequence with a single index, the database server USES the index to read the rows in the ordered sequence, thus avoiding a sort.

如果该子句中所有的列都是以用单个索引要求的顺序出现的，那么数据库服务器就使用索引来按顺序读取行，因而避免了排序。

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As we all know due to the number of times we are not charged sales tax for items ordered online or via catalogs, Congress has not exercised its authority under the commerce clause to change the Quill result.

FORBES: After Twenty Years Congress Still Has Not Acted On Sales Tax