Exemplo Criação Função

CREATE OR REPLACE FUNCTION pega_sal
(p_id IN employees_bkp.employee_id%TYPE)
RETURN NUMBER
IS
v_sal employees_bkp.salary%TYPE :=0;
BEGIN
SELECT salary
INTO v_sal
FROM cristiano.employees_bkp
WHERE employee_id = p_id;
RETURN v_sal;
END pega_sal;

Executando Função:

VARIABLE g_sal NUMBER

EXECUTE :g_sal := pega_sal(100)

PRINT g_sal