#foreign key (MUL): 可以理解成外部有一个硬性限制 b、分表 + foreign key + on update cascade on delete cascade: 有硬性限制,对被关联表进行修改删除,关联表相应元素跟着改变;强耦合 c、分表: 靠逻辑上的关系维护,解开耦合 二、表与表之间的关系(两张表之间单向的多对一关系,称为多对一) i、a True...
PRIMARYKEY(`id`), 12 KEY`dage_id` (`dage_id`),//在dage_id上有索引,名字叫dage_id 13 CONSTRAINT`xiaodi_ibfk_1`FOREIGNKEY(`dage_id`)REFERENCES`dage` (`id`) 14 ) ENGINE=InnoDBDEFAULTCHARSET=latin1; 插入个大哥: 1 mysql>insertintodage(name)values('铜锣湾'); 2 Query OK,1row affected ...
-> FOREIGN KEY order_f_key (u_id) REFERENCES user(id) //创建外键 -> )ENGINE=innodb DEFAULT CHARSET=utf8 AUTO_INCREMENT=1; //innodb引擎 Query OK, 0 rows affected, 1 warning (0.06 sec) mysql> INSERT INTO `order` (`u_id`, `username`, `money`, `datetime`) VALUES ('1', 'tank'...
Table: Info > ID, Text > 20, Toni > 30, Mahoni > 40, Hamburg > 150, red I need a Select that brings me that result: 1, Toni, Mahoni, Hamburg, ... 3, ... red, The door How do I have to create the tables and how the query? I need urgend helpNavigate...
KEY`dage_id` (`dage_id`), 13 CONSTRAINT`xiaodi_ibfk_1`FOREIGNKEY(`dage_id`)REFERENCES`dage` (`id`) 14 ) ENGINE=InnoDBDEFAULTCHARSET=latin1; 插入个大哥: 1 mysql>insertintodage(name)values('铜锣湾'); 2 Query OK,1row affected (0.01sec) ...
mysql> create table grade( -> grade_year year primary key, -> name varchar(20) not null -> )engine=innodb; Query OK, 0 rows affected (0.85 sec) mysql> create table student( -> id int primary key, -> name varchar(20) not null, ...
insert into empvalues(2,'李四',1005);//添加从表记录失败ERROR1452(23000):Cannot add(添加) or update(修改) a child row:a foreign key constraintfails(`atguigudb`.`emp`,CONSTRAINT`emp_ibfk_1`FOREIGNKEY(`deptid`)REFERENCES`dept`(`did`))//从表emp添加记录失败,因为主表dept没有1005部门mysql>se...
mysql> create table orders (id int(11) primary key ,userId int(11) , FOREIGN KEY (userId) REFERENCES user(id) ); Query OK, 0 rows affected, 2 warnings (0.06 sec) mysql> insert orders values(1,3); ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint ...
mysql> CREATE TABLE slave (cust_id int(11),cust_name int(11),cust_email char(255),cust_address char(50),PRIMARY KEY(cust_id),CONSTRAINT call_name FOREIGN KEY(cust_name) REFERENCES master(cust_id));Query OK, 0 rows affected (0.04 sec)重新创建slave数据表。注意！cust_name字段熟悉为int...
FOREIGN KEY (`userId`) REFERENCES `User`(`id`) ON DELETE SET DEFAULT ON UPDATE SET DEFAULT; INSERT INTO `User`(`id`) VALUES (1); INSERT INTO `User`(`id`) VALUES (3); INSERT INTO `Post`(`id`, `userId`) VALUES (1, 1); ...