1、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));
2、刪除表中已有的主鍵約束
(1)無命名
可用 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);
摘自:http://yyuhui-qq-com.javaeye.com/blog/748007