> For the complete documentation index, see [llms.txt](https://docs.postgresql.tw/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.postgresql.tw/13/the-sql-language/index.md).

# 11. 索引（Index）

索引是增強資料庫效能的常用方法。索引允許資料庫伺服器比沒有索引時更快地查詢和檢索特定資料列。但索引也會增加整個資料庫系統的開銷，因此應該合理地使用它們。


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