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- Table of Contents
- Query Language (SQL) Functions
- Programming Language Functions
As it turns out, part of defining a new type is the definition
of functions that describe its behavior. Consequently, while it is
possible to define a new function without defining a new type, the
reverse is not true. We therefore describe how to add new functions
to Postgres before describing how to add new types. Postgres SQL
provides two types of functions: query language functions
(functions written in SQL and programming language functions
(functions written in a compiled programming language such as C.)
Either kind of function can take a base type, a composite type or
some combination as arguments (parameters). In addition, both kinds
of functions can return a base type or a composite type. It's
easier to define SQL functions, so we'll start with those. Examples
in this section can also be found in funcs.sql and C-code/funcs.c.
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