SQL复合主键[多条件][批量]增删改查

CREATE TABLE `users` (
  `class_id` int NOT NULL,
  `user_id` int NOT NULL,
  `user_name` varchar(40) DEFAULT NULL,
  `money_out` int DEFAULT NULL,
  PRIMARY KEY (`class_id`,`user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb3;

INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (1, 1, '张一一', 1000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (1, 2, '张一二', 2000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (1, 3, '张一三', 3000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (2, 1, '张二一', 4000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (2, 2, '张二二', 5000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (2, 3, '张二三', 6000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (3, 1, '张三一', 7000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (3, 2, '张三二', 8000);
INSERT INTO `users`(`class_id`, `user_id`, `user_name`, `money_out`) VALUES (3, 3, '张三三', 9000);

select * from `users`;

select COUNT(*) from users;

select * from `users` where `class_id` = 1 and `user_id`=2;

insert into `users`(`class_id`, `user_id`, `user_name`, `money_out`) values(1, 1, '张一一', 1000);

replace into `users`(`class_id`, `user_id`, `user_name`, `money_out`) values(3, 3, '张三三', 9000);

delete from `users` where `class_id` = 1; 

delete from `users` where `class_id` = 2 and `user_id` = 2; 

    --     查询班级1，用户1和3
    select * from `users` where `class_id` = 1 and `user_id` in(1,3);

    -- 刪除班级2，用户1和3
    delete from `users` where `class_id` = 2 and `user_id` in (1,3);

    -- 修改班级3，用户1,3的money都为200

    update  `users` set money_out=200  where `class_id` = 3 and `user_id` in(1,3);