create table grade (Sid int(8),Cid int(10),score int,index(Sid),foreign key (Sid) references student(id) on delete restrict on update cascade)ENGINE=InnoDB; 在上述SQL语句中,on delete restrict 是指明在删除时外键会对该删除操作进行限制,而on update cascade是指名在更新时会对该更新操作进行同步。
create table grade (Sid int(8),Cid int(10),score int,index(Sid),foreign key (Sid) references student(id) on delete restrict on update cascade)ENGINE=InnoDB; 在上述SQL语句中,on delete restrict 是指明在删除时外键会对该删除操作进行限制,而on update cascade是指名在更新时会对该更新操作进行同步。
foreign key(user_id) references user(id), foreign key(host_id) references host(id) ); 练习: #班级表cid caption#学生表sid sname gender class_id#老师表tid tname#课程表cid cname teacher_id#成绩表sid student_id course_id number
修改表ORDERS,增加 fk_orders1的设置一个外键为customer_sid，是参照CUSTOMER的sid列名。
mysql> create table t3(id int default 1); mysql> alter table t3 modify id int not null default 1; ===综合练习=== mysql> create table student( -> name varchar(20) not null, -> age int(3) unsigned not null default 18, -> sex enum('male','female') default 'male'...
SQL FOREIGN KEY 约束 SQL FOREIGN KEY 约束用于防止破坏表之间关系的操作。FOREIGN KEY 是一张表中的字段(或字段集合),它引用另一张表中的主键。...具有外键的表称为子表,具有主键的表称为被引用表或父表。...FOREIGN KEY 约束防止将无效数据插入到外键列中,因为它必
(`id`) USING HASH ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET...碰到错误 在创建外键之时,使用的SQL和碰到错误信息如下: alter table `product' add CONSTRAINT `sid_ref` FOREIGN KEY (`sid`)...REFERENCES `sealer` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION 碰到的错误信息如下: ...
This article presents the results of a quantitative and qualitative study of the judgments of the Polish Constitutional Tribunal in terms of the presence of references to the judgments of other constitutional courts. Reference by the Tribunal to foreign constitutional jurisprudence is a rela...
Creation of foreign key in the new table: CREATE TABLE "Course Schedule"( Sid int Not Null Primary Key, WeekDay varchar(255), scheduleTime varchar(255), id int References student(id) ) In the above example, “id” column in the “Course Schedule” table is a foreign key in the “Cou...
KEY(cname), -> CONSTRAINT Class_insid_fk FOREIGN KEY(insid) REFERENCES Instructor(insid)); mysql> CREATE TABLE Enrolled ( -> sid INTEGER, -> cname VARCHAR(25), -> CONSTRAINT Enrolled_sid_cname_pk PRIMARY KEY(sid,cname), -> CONSTRAINT Enrolled_sid_fk FOREIGN KEY(sid) REFERENCES Student(...