mysql自定义函数多参数_自定义mysql函数 - 无法传递参数

作为标题状态。这里的功能

DELIMITER //

CREATE FUNCTION GetCreateValue( table_name CHAR(64), id_field CHAR(64), name_field CHAR(64), name_value CHAR(64) )

RETURNS INTEGER

BEGIN

DECLARE ret INTEGER;

SELECT count(*) INTO ret FROM table_name WHERE name_field = name_value;

IF ret < 1 THEN

INSERT INTO table_name SET name_field = name_value;

SELECT id_field INTO ret FROM table_name WHERE name_field = name_value;

ELSE

SELECT id_field INTO ret FROM table_name WHERE name_field = name_value;

END IF;

RETURN ret;

END//

DELIMITER ;当我运行类似的东西时

SELECT GetCreateValue('table1', 'ID', 'name', '123456');我得到一个表“table_name”不存在的错误。显然参数没有通过。为什么？