索引是单列主键还是多列主键？查重复值是怎么查询出来的？

SQL> create table test11(id int,name varchar2(20));

Table created.

SQL> create index p_test11 on test11(id);

Index created.

SQL> insert into test11 values(1,‘user1’);

1 row created.

SQL> insert into test11 values(1,‘user1’);

1 row created.

SQL> commit;

Commit complete.

SQL> alter table test11 add constraint uk_t_1 unique (id) deferrable enable novalidate;

Table altered.

如果主键创建时按照这种方式是可以出现重复值的。