The ST_INFO master table has millions of rows that are updated very rarely. It has a STATE_CODE column that contains the value for 25 states. The table is frequently queried on the STATE_CODE column. Which type of index would you suggest to improve the query performance？（）
- A、B-tree
- B、bitmap
- C、reverse key
- D、function based
正确答案:B
答案解析:有
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