Oracle中給表添加主鍵、外鍵

一、創建表的同時創建主鍵約束

1、無命名

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、刪除表中已有主鍵約束

1、無命名可用

SELECT * from user_cons_columns;

SELECT * from user_cons_columns;

查找表中主鍵名稱得student表中的主鍵名爲SYS_C002715  

alter table student drop constraint SYS_C002715;

2、有命名

alter table students drop constraint yy;

3、向表中添加主鍵約束

alter table student add constraint pk_student primary key(studentid);

4、向表中添加外鍵約束

ALTER TABLE table_A ADD CONSTRAINT FK_name FOREIGN KEY(id) REFERENCES table_B(id);