SQL 질문드립니다..

/*

gold’ 등급의 고객명과 적립금, 등급별 적립금 평균과의 차액 리스트를 적립금에 대해 내림차순으로

출력하려고 할때 등급별 적립금 평균과의 차액 리스트를 어떤식으로 작성해야 할까요..?
*/

CREATE TABLE `test1` (
    `NO` INT(11) NOT NULL AUTO_INCREMENT,
    `id` VARCHAR(20) NULL DEFAULT '' COLLATE 'utf8_general_ci',
    `name` VARCHAR(30) NULL DEFAULT '' COLLATE 'utf8_general_ci',
    `age` VARCHAR(30) NULL DEFAULT '' COLLATE 'utf8_general_ci',
    `LEVEL` VARCHAR(30) NULL DEFAULT '' COLLATE 'utf8_general_ci',
    `job` VARCHAR(30) NULL DEFAULT '' COLLATE 'utf8_general_ci',
    `point` INT(11) NULL DEFAULT '0',
    PRIMARY KEY (`NO`) USING BTREE
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
;


INSERT INTO `test1` (`NO`, `id`, `name`, `age`, `LEVEL`, `job`, `point`) VALUES (1, 'apple', '정소화', '20', 'gold', '학생', 1000);
INSERT INTO `test1` (`NO`, `id`, `name`, `age`, `LEVEL`, `job`, `point`) VALUES (2, 'banana', '김선우', '25', 'vip', '간호사', 2500);
INSERT INTO `test1` (`NO`, `id`, `name`, `age`, `LEVEL`, `job`, `point`) VALUES (3, 'carrot', '고명석', '28', 'gold', '교사', 4500);
INSERT INTO `test1` (`NO`, `id`, `name`, `age`, `LEVEL`, `job`, `point`) VALUES (4, 'melon', '성원용', '35', 'gold', '회사원', 5000);
INSERT INTO `test1` (`NO`, `id`, `name`, `age`, `LEVEL`, `job`, `point`) VALUES (5, 'orange', '김용욱', '22', 'silver', '학생', 0);
INSERT INTO `test1` (`NO`, `id`, `name`, `age`, `LEVEL`, `job`, `point`) VALUES (6, 'peach', '오형준', 'NULL', 'silver', '의사', 300);
INSERT INTO `test1` (`NO`, `id`, `name`, `age`, `LEVEL`, `job`, `point`) VALUES (7, 'pear', '채광주', '31', 'silver', '회사원', 500);

SELECT  
    a.id,
    a.name,
    a.age,
    a.job,
    a.level,
    a.point,
    (
        (
            SELECT 
                SUM(POINT) sp 
            FROM test1 b
            WHERE LEVEL = a.`LEVEL`
        ) / 
        (
            SELECT 
                COUNT(LEVEL) 
            FROM test1 b
            WHERE LEVEL = a.`LEVEL`
        )
    ) AS AVG
    ,
    a.point - (
        (
            SELECT 
                SUM(POINT) sp 
            FROM test1 b
            WHERE LEVEL = a.`LEVEL`
        ) / 
        (
            SELECT 
                COUNT(LEVEL) 
            FROM test1 b
            WHERE LEVEL = a.`LEVEL`
        )
    ) AS cha
FROM test1 a
ORDER BY cha;