MySQL user auth with stored procedures

users.sql

/*

Possible SHA1 values 2^160 = 1.46150164 × 10^48

RAND() returns a float from 0 to 1 ~= 10^16

CONCAT(RAND(), RAND(), RAND())

*/

SELECT LENGTH(UNHEX(SHA(RAND())));

DROP TABLE users;
CREATE TABLE users (
	id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
	name VARCHAR(32) NOT NULL UNIQUE,
	salt BINARY(20) NOT NULL,
	hash BINARY(20) NOT NULL
) ENGINE = INNODB;

DELIMITER //

DROP PROCEDURE user_auth //
CREATE PROCEDURE user_auth(IN name CHAR(32), IN pass CHAR(64))
BEGIN
	SELECT users.id, users.name, users.salt INTO @id, @name, @salt FROM users WHERE users.name = name;
	IF (SELECT COUNT(users.id) FROM users WHERE users.name = name AND users.hash = UNHEX(SHA1(CONCAT(HEX(@salt), pass)))) != 1 THEN
		SET @message_text = CONCAT('Login incorrect for user \'', @name, '\'');
		SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = @message_text;
	ELSE
		SELECT @id AS id, @name AS name;
	END IF;
END//

DROP PROCEDURE user_create //
CREATE PROCEDURE user_create(IN name CHAR(32), IN pass CHAR(64))
BEGIN
	IF (SELECT COUNT(users.id) FROM users WHERE users.name = name) > 0 THEN
		SET @message_text = CONCAT('User \'', name, '\' already exists');
		SIGNAL SQLSTATE '45000' SET MESSAGE_TEXT = @message_text;
	ELSE
		SET @salt = UNHEX(SHA1(CONCAT(RAND(), RAND(), RAND())));
		INSERT INTO users(name, salt, hash) VALUES (name, @salt, UNHEX(SHA1(CONCAT(HEX(@salt), pass))));
		CALL user_auth(name, pass);
	END IF;
END//

DELIMITER ;

DROP USER 'doobrymedia'@'localhost';
CREATE USER 'doobrymedia'@'localhost' IDENTIFIED BY 'secret';
GRANT EXECUTE ON PROCEDURE doobrymedia.user_auth TO 'doobrymedia'@'localhost';
GRANT EXECUTE ON PROCEDURE doobrymedia.user_create TO 'doobrymedia'@'localhost';

CALL user_create('chris', SHA1('secret'));
CALL user_create('chris', SHA1('secret'));
CALL user_create('chris', SHA1('secret'));
CALL user_create('chris', SHA1('secret'));
CALL user_create('chris', SHA1('secret'));
CALL user_create('seonaid', SHA1('secret'));
CALL user_auth('chris', SHA1('secret'));
CALL user_auth('chris', SHA1('secret2'));

What are the benefits of create two separate procs?