Positional Parameters

Used in function definitions and prepared queries to reference values supplied externally to an SQL statement.

Are of the form $number e.g.

mydb=> CREATE FUNCTION sum_modulo_n(a int, b int, n int DEFAULT 10) RETURNS int AS
mydb->   'SELECT ($1 + $2) % $3' LANGUAGE SQL;  -- function body with positional params
mydb=> SELECT sum_modulo_n(1, 2), sum_modulo_n(1, 2, 3);
 sum_modulo_n | sum_modulo_n 
--------------+--------------
            3 |            0
(1 row)