---
title: "User-Defined Procedures"
id: xproc
pg_version: "20devel"
---

<a id="xproc"></a>

## 36.4. User-Defined Procedures

A procedure is a database object similar to a function. The key differences are: 
-  Procedures are defined with the [`CREATE PROCEDURE`](sql-createprocedure.md) command, not `CREATE FUNCTION`. 
-  Procedures do not return a function value; hence `CREATE PROCEDURE` lacks a `RETURNS` clause. However, procedures can instead return data to their callers via output parameters. 
-  While a function is called as part of a query or DML command, a procedure is called in isolation using the [`CALL`](sql-call.md) command. 
-  A procedure can commit or roll back transactions during its execution (then automatically beginning a new transaction), so long as the invoking `CALL` command is not part of an explicit transaction block. A function cannot do that. 
-  Certain function attributes, such as strictness, don't apply to procedures. Those attributes control how the function is used in a query, which isn't relevant to procedures. 

 

The explanations in the following sections about how to define user-defined functions apply to procedures as well, except for the points made above. 

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