2022-12-15：寻找用户推荐人。写一个查询语句，返回一个客户列表，列表中客户的推荐人的编号都 不是 2。 对于示例数据，结果为： +------+ | name | +------+ | Wil

DROP TABLE IF EXISTS `customer`;CREATE TABLE `customer` (  `id` int(11) NOT NULL,  `name` varchar(255) NOT NULL,  `referee_id` int(11) DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB DEFAULT CHARSET=latin1;
INSERT INTO `customer` VALUES ('1', 'Will', null);INSERT INTO `customer` VALUES ('2', 'Jane', null);INSERT INTO `customer` VALUES ('3', 'Alex', '2');INSERT INTO `customer` VALUES ('4', 'Bill', null);INSERT INTO `customer` VALUES ('5', 'Zack', '1');INSERT INTO `customer` VALUES ('6', 'Mark', '2');

SELECT name FROM customer WHERE referee_id != 2 OR referee_id IS NULL;