如何将NULL输入参数限制为oracle存储过程

CREATE OR REPLACE PROCEDURE your_procedure (
    p_input_parameter IN VARCHAR2,
    p_dummy OUT VARCHAR2
)
AS
BEGIN
    p_dummy := p_input_parameter; /* 将参数原样返回 */

    IF NVL(p_input_parameter, 'NULL') != 'NULL' THEN
        p_dummy := p_input_parameter;
    END IF;
END your_procedure;

CREATE OR REPLACE PROCEDURE your_procedure (
    p_input_parameter IN VARCHAR2,
    p_dummy OUT VARCHAR2
)
AS
BEGIN
    p_dummy := p_input_parameter; /* 将参数原样返回 */

    IF NVL(p_input_parameter, 'NULL') != 'NULL' THEN
        p_dummy := NVL(p_input_parameter, p_input_parameter);
    END IF;
END your_procedure;

CREATE OR REPLACE PROCEDURE your_procedure (
    p_input_parameter IN RAW,
    p_dummy OUT RAW
)
AS
BEGIN
    p_dummy := p_input_parameter; /* 将参数原样返回 */

    IF NVL(RAWTOHEX(p_input_parameter), '00') != '00' THEN
        p_dummy := p_input_parameter;
    END IF;
END your_procedure;