# 37.4. User-defined Procedures

A procedure is a database object similar to a function. The difference is that a procedure does not return a value, so there is no return type declaration. While a function is called as part of a query or DML command, a procedure is called explicitly using the [CALL](https://www.postgresql.org/docs/11/sql-call.html) statement.

The explanations on how to define user-defined functions in the rest of this chapter apply to procedures as well, except that the [CREATE PROCEDURE](https://www.postgresql.org/docs/11/sql-createprocedure.html) command is used instead, there is no return type, and some other features such as strictness don't apply.

Collectively, functions and procedures are also known as *routines*. There are commands such as [ALTER ROUTINE](https://www.postgresql.org/docs/11/sql-alterroutine.html) and [DROP ROUTINE](https://www.postgresql.org/docs/11/sql-droproutine.html) that can operate on functions and procedures without having to know which kind it is. Note, however, that there is no `CREATE ROUTINE` command.


---

# 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/14/server-programming/extending-sql/user-defined-procedures.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.