34.3. User-Defined Functions

PostgreSQL provides four kinds of functions:

Every kind of function can take base types, composite types, or some combination as arguments (parameters). In addition, every kind of function can return a base type or a composite type.

It's easiest to define SQL functions, so we'll start with those. Examples in this section can also be found in funcs.sql and funcs.c in the tutorial directory.

Throughout this chapter, it can be useful to look at the reference page of the CREATE FUNCTION command to understand the examples better.