Oracle中给表添加主键、外键
1、创建表的同时创建主键约束
(1)无命名 create table student ( studentid int primary key not null, studentname varchar(8), age int);
(2)有命名 create table students ( studentid int , studentname varchar(8), age int, constraint yy primary key(studentid));
2、删除表中已有的主键约束
(1)无命名可用 SELECT * from user_cons_columns; 查找表中主键名称得student表中的主键名为SYS_C002715 alter table student drop constraint SYS_C002715;
(2)有命名 alter table students drop constraint yy;
3、向表中添加主键约束 alter table student add constraint pk_student primary key(studentid);
4、向表中添加外键约束 ALTER TABLE table_A ADD CONSTRAINT FK_name FOREIGN KEY(id) REFERENCES table_B(id);
下面举个创建表的同时创建外键的例子:
两张表 A B
A内有主键ID
B内有外键A_ID
怎么把这两张表创建主外键关系??
create TABLE zhao( id number primary key, mingcheng nvarchar2(50), neirong nvarchar2(50), jiezhiriqi date, zhuangtai nvarchar2(50) ); create TABLE tou( id number primary key, zhao_id number, toubiaoqiye nvarchar2(50), biaoshuneirong nvarchar2(50), toubiaoriqi date, baojia number, zhuangtai nvarchar2(50), foreign KEY(zhao_id) REFERENCES zhao(id) );
references 不是
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