CONSTRAINT`s_id`FOREIGN KEY (`student_id`) REFERENCES`student`(`id`) ) 3 更改事件触发限制为 CASCADE #删除旧的外键 ALTERTABLEstudent_scoreDROPFOREIGNKEY s_id; #添加新的外键,修改事件触发限制为 CASCADE ALTERTABLEstudent_score ADDCONSTRAINTs_idFOREIGNKEY (student_id)REFERENCESstudent (id) ONDELETEC...
列名int, primary key clustered(id asc) with(ignore_dup_key=off) on [primary], --主键索引声明 constraint 外键名 foreign key(列名) references 主表名(列名) on update cascade--是否级联操作 on delete cascade )on [primary] --字段注释声明 exec sys.sp_addextendedproperty @name=N'MS_Description',...
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`test`.`t_user`, CONSTRAINT `t_user_ibfk_1` FOREIGN KEY (`groupid`) REFERENCES `t_group` (`id`) ON DELETE CASCADE ON UPDATE CASCADE) 级联测试: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ...
-> foreign key(repo_id) -> references repo_table(repo_id) -> on delete cascade -> on update cascade; --- ENGINE=InnoDB DEFAULT CHARSET=gb2312; //另一种方法,可以替换type=innodb; 3、相关操作 外键约束(表2)对父表(表1)的含义: 在父表上进行update/delete以更新或删除在子表中有一条或多...
CREATE TABLE orders ( id INT PRIMARY KEY, customer_name VARCHAR(255) ); CREATE TABLE order_items ( id INT PRIMARY KEY, order_id INT, product_name VARCHAR(255), FOREIGN KEY (order_id) REFERENCES orders(id) ON DELETE CASCADE ); 在这个示例中,我们在创建order_items表时,通过ON DELETE CASCAD...
前一种情况,在外键定义中,我们使用ON UPDATE CASCADE ON DELETE RESTRICT;后一种情况,可以使用ON UPDATE CASCADE ON DELETE CASCADE。 InnoDB允许你使用ALTER TABLE在一个已经存在的表上增加一个新的外键: ALTER TABLE tbl_name ADD [CONSTRAINT [symbol]] FOREIGN KEY [index_name] (index_col_name, ...) RE...
修改外键约束:将外键约束的ON DELETE子句修改为CASCADE、SET NULL或SET DEFAULT,以允许删除操作。 手动删除子表记录:在删除父表记录之前,先手动删除子表中与之相关的记录。 示例代码(修改外键约束): 代码语言:txt 复制 ALTER TABLE child DROP FOREIGN KEY fk_child_parent; ALTER TABLE child ADD FOREIGN KEY (...
FOREIGN KEY (parent_id) REFERENCES parent_table(id) ON DELETE CASCADE ON UPDATE CASCADE; 2. NO ACTION(无动作/默认行为) 行为描述:在MySQL中,NO ACTION实际上等同于RESTRICT,这意味着如果试图删除或更新父表中一行数据,而该行在子表中有对应关联项,操作会被拒绝,以防止违反外键约束。
05 sec) ## 为两张表增加外键 mysql> alter table l1 add CONSTRAINT foreign key (l2id) REFERENCES l2(l2id) ON DELETE CASCADE; Query OK, 5 rows affected (0.14 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> alter table l2 add CONSTRAINT foreign key (l1id) REFERENCES l1(l1id) ON ...
[CONSTRAINT symbol] FOREIGN KEY [id] (index_col_name, ...) REFERENCES tbl_name (index_col_name, ...) [ON DELETE {RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT}] [ON UPDATE {RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT}] ...