The DB2 9.5 optimizer USES both type of indexes to optimize the queries and help selecting the best plan for query execution.

DB 2 9.5优化器使用两种类型的索引来优化查询，并帮助选择最佳的查询执行计划。

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When the query is prepared, the database will analyze, compile and optimize it's plan for executing the query.

当查询准备好后，数据库将分析、编译和优化执行该查询的计划。

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And when I check on the SQL query execution plan, it seems to be pretty inconsistent in how SQL tries to optimize this query.

当我检查的SQL查询执行计划，这似乎是很不一致的方式试图优化这个查询的SQL。

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