Explain recursive subprograms in PL/SQL

Recursion works in PL/SQL like any language: define a base case that returns without recursing, and a recursive case that moves toward it. Each invocation has its own locals. Depth is bounded by the PL/SQL stack, so very deep recursion (tens of thousands of frames) can raise ORA-06500 / storage errors — an iterative version or a hierarchical SQL query (CONNECT BY / recursive WITH) is better for deep tree walks.

CREATE OR REPLACE FUNCTION factorial(p_n PLS_INTEGER) RETURN NUMBER IS
BEGIN
  IF p_n <= 1 THEN
    RETURN 1;                       -- base case
  ELSE
    RETURN p_n * factorial(p_n - 1);  -- recursive case
  END IF;
END;
/
SELECT factorial(10) FROM dual;   -- 3628800