How to retrieve numeric indexes from enum type values in MySQL

Example usage is like the following:

CREATE TABLE persons(
	id INT NOT NULL AUTO_INCREMENT,
	name CHAR(30) NOT NULL,
	surname CHAR(30) NOT NULL,
	gender ENUM('male','female','unisex') NOT NULL,
	PRIMARY KEY (id,gender)
);

INSERT INTO persons(name,surname,gender) VALUES('erman','gülhan','male'),('ayşe','dolu','female'),('ali','veli','male');

# this returns gender as string
SELECT name,gender FROM persons;

# this returns gender as numeric index
SELECT name,gender+0 FROM persons;