... 选择追踪程序 selective tracing routine; 选择子句 choice clause; 选择字块 selector block; ...
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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。
Therefore, you may often choose to implement indexes that include only the columns referred to in the WHERE and ORDER BY clauses.
如果使用标准的into子句，那么按选择的字段的次序填充行。
If you use the standard INTO clause, the row is filled in the order of the selected fields.
这个更新并不使用SQL where子句选择特定的一行。
This update does not use an SQL WHERE clause to select a specific row.
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