Oracle中给表添加主键、外键

一、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));

二、删除表中已有主键约束

1、无命名可用

SELECT * from user_cons_columns;

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);