# 11. 索引（Index）

索引是一種強化資料庫效能常用的方法。索引可以讓資料庫比沒有索引時更快地查詢和檢索特定的資料。然而，索引也會增加整個資料庫系統的負擔，因此應該合理地使用它們。


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# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.postgresql.tw/16/the-sql-language/index.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.
