使用索引的误区之二：使用了 和 != 操作符，导致查询不使用索引[6]

| id  | operation            |  name       | rows  | bytes | cost  |

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|   0 | select statement     |             |       |       |       |

|*  1 |  table access full   | dept        |       |       |       |

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predicate information (identified by operation id):

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   1 - filter("dept"."dname"<>'developer')

note: rule based optimization

14 rows selected

将条件修改为“dname <'developer' and dname>'developer'”，则可以使用索引

select deptno from dept where dname <'developer' and dname>'developer';

plan_table_output