Chapter 9. Functions and Operators
第九章.函數和操作符
PostgreSQL provides a large number of functions and operators for the built-in data types. Users can also define their own functions and operators, as described in Part V. The psql commands \df and \do can be used to list all available functions and operators, respectively.
PostgreSQL爲內置數據類型提供了大量函數和運算符。 用戶還可以定義自己的函數和運算符，如第五部分所述。psql命令\df和\do可分別用於列出所有可用的函數和運算符。
If you are concerned about portability then note that most of the functions and operators described in this chapter, with the exception of the most trivial arithmetic and comparison operators and some explicitly marked functions, are not specified by the SQL standard. Some of this extended functionality is present in other SQL database management systems, and in many cases this functionality is compatible and consistent between the various implementations. This chapter is also not exhaustive;additional functions appear in relevant sections of the manual.
如果您擔心可移植性，那麼請注意，本章介紹的大多數函數和運算符，除最常用的算術和比較運算符以及一些顯式標記的函數外，SQL標準均未指定。此擴展功能中的某些功能存在於其他SQL數據庫管理系統中，並且在許多情況下，此功能在各種實現之間是兼容且一致的。 本章未盡之處；可在手冊的相關章節中查看。