MySQL去重保留最大的那条记录（取最新的记录）

-- 以用户登录日志表为例，取用户最近登录的设备   SET NAMES utf8mb4; SET FOREIGN_KEY_CHECKS = 0;    -- ----------------------------  -- Table structure for t_login_log  -- ----------------------------  DROP TABLE IF EXISTS `t_login_log`;  CREATE TABLE `t_login_log` (    `id` INT(11) NOT NULL AUTO_INCREMENT,    `user_id` INT(11) NOT NULL COMMENT '用户ID',    `device_name` VARCHAR(32) COLLATE utf8mb4_bin NOT NULL COMMENT '登录设备',    `login_time` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP COMMENT '登录时间',    PRIMARY KEY (`id`)  ) ENGINE=INNODB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;    -- ----------------------------  -- Records of t_login_log  -- ----------------------------  BEGIN;  INSERT INTO `t_login_log` VALUES (1, 1121, 'iPhone 6s', '2019-07-01 19:20:25');  INSERT INTO `t_login_log` VALUES (2, 2120, 'vivo x20', '2019-06-28 16:21:11');  INSERT INTO `t_login_log` VALUES (3, 1607, 'huawei P30', '2019-07-04 19:21:59');  INSERT INTO `t_login_log` VALUES (4, 2120, 'vivo x20', '2019-06-30 19:22:34');  INSERT INTO `t_login_log` VALUES (5, 2120, 'vivo x20', '2019-07-04 19:23:07');  INSERT INTO `t_login_log` VALUES (6, 1121, 'iPad mini', '2019-07-03 19:23:25');  INSERT INTO `t_login_log` VALUES (7, 1607, 'iPhone 8 Plus', '2019-06-30 19:24:06');  INSERT INTO `t_login_log` VALUES (8, 1970, 'MI8', '2019-07-03 19:25:00');  COMMIT;    SET FOREIGN_KEY_CHECKS = 1;    -- 自连接，取最新的记录 SELECT * FROM t_login_log ORDER BY user_id;   SELECT    t1.*   FROM t_login_log t1   LEFT JOIN t_login_log t2 ON t1.user_id = t2.user_id AND t1.login_time < t2.login_time   WHERE t2.id IS NULL;