SQLite does not have a stored function/stored procedure language. So CREATE FUNCTION does not work. What you can do though is map functions from a c library to SQL functions (user-defined functions). To do that, use SQLite’s C API (see: http://www.sqlite.org/c3ref/create_function.html)
If you’re not using the C API, your wrapper API may define something that allows you access to this feature, see for example:
- PHP
sqlite_create_function()(http://www.php.net/manual/en/function.sqlite-create-function.php) - Python
sqlite3.create_function()(http://docs.python.org/3/library/sqlite3.html#sqlite3.Connection.create_function) - Perl
$dbh->sqlite_create_function($name,$argc,$code_ref,$flags)(https://metacpan.org/pod/DBD::SQLite#$dbh-%3Esqlite_create_function(-$name,-$argc,-$code_ref,-$flags-))