In this case, the optimizer USES a generic rule or a default value to estimate an average cost by assuming normal data distribution.

在这种情况下，优化器会使用一个通用规则或者默认值以正常数据分布率来评估得到一个平均开销值。

youdao

If multiple indexes are defined on the table, the optimizer USES the index that can rule out the most data in the table.

如果表上定义了多个索引，那么优化器就使用可以排除表中最多数据的索引。

youdao

In this example, the first thing the optimizer does is to evaluate the condition that state equals NEVADA, because that will rule out a large number of data rows in the table.

本例中，优化器所做的第一件事就是评估state等于NEVADA的这个条件，因为这将排除表中的大量数据行。

youdao

In this example, the first thing the optimizer does is to evaluate the condition that state equals NEVADA, because that will rule out a large number of data rows in the table.

本例中，优化器所做的第一件事就是评估state等于NEVADA的这个条件，因为这将排除表中的大量数据行。

youdao