分2种情况进行测试：

1.创建表时直接创建的主键。建表语句如下：

CREATE TABLE EMP
       (EMPNO NUMBER(4) CONSTRAINT PK_EMP PRIMARY KEY,
        ENAME VARCHAR2(10),
        JOB VARCHAR2(9),
        MGR NUMBER(4),
        HIREDATE DATE,
        SAL NUMBER(7,2),
        COMM NUMBER(7,2),
        DEPTNO NUMBER(2) CONSTRAINT FK_DEPTNO REFERENCES DEPT);

SQL> l
  1* select table_owner,index_name,index_type,table_name from user_indexes where table_name='EMP'
SQL> /
 
TABLE_OWNER                    INDEX_NAME                     INDEX_TYPE                  TABLE_NAME
------------------------------ ------------------------------ --------------------------- ------------------------------
SCOTT                          IDX_JOB                        NORMAL                      EMP
SCOTT                          IDX_JOB_MGR                    NORMAL                      EMP
SCOTT                          IDX_MGR                        NORMAL                      EMP
SCOTT                          PK_EMP                         NORMAL                      EMP
 
SQL> select owner,constraint_name,constraint_type,table_name,status from user_constraints where table_name='EMP';
 
OWNER                          CONSTRAINT_NAME                C TABLE_NAME                     STATUS
------------------------------ ------------------------------ - ------------------------------ --------
SCOTT                          PK_EMP                         P EMP                            ENABLED
SCOTT                          FK_DEPTNO                      R EMP                            ENABLED
 
SQL> alter table emp modify constraint pk_emp disable;
 
Table altered.
 
SQL> select table_owner,index_name,index_type,table_name from user_indexes where table_name='EMP'
  2  ;
 
TABLE_OWNER                    INDEX_NAME                     INDEX_TYPE                  TABLE_NAME
------------------------------ ------------------------------ --------------------------- ------------------------------
SCOTT                          IDX_JOB                        NORMAL                      EMP
SCOTT                          IDX_JOB_MGR                    NORMAL                      EMP
SCOTT                          IDX_MGR                        NORMAL                      EMP
 
SQL>  select owner,constraint_name,constraint_type,table_name,status from user_constraints where table_name='EMP';
 
OWNER                          CONSTRAINT_NAME                C TABLE_NAME                     STATUS
------------------------------ ------------------------------ - ------------------------------ --------
SCOTT                          PK_EMP                         P EMP                            DISABLED
SCOTT                          FK_DEPTNO                      R EMP                            ENABLED

       从上述过程可以看出，这种情况下，将主键disable后，相应的索引也被删除。此时再将主键enable：

SQL> alter table emp modify constraint pk_emp enable;
 
Table altered.
 
SQL>  select owner,constraint_name,constraint_type,table_name,status from user_constraints where table_name='EMP';
 
OWNER                          CONSTRAINT_NAME                C TABLE_NAME                     STATUS
------------------------------ ------------------------------ - ------------------------------ --------
SCOTT                          PK_EMP                         P EMP                            ENABLED
SCOTT                          FK_DEPTNO                      R EMP                            ENABLED
 
SQL> select table_owner,index_name,index_type,table_name from user_indexes where table_name='EMP';
 
TABLE_OWNER                    INDEX_NAME                     INDEX_TYPE                  TABLE_NAME
------------------------------ ------------------------------ --------------------------- ------------------------------
SCOTT                          IDX_JOB                        NORMAL                      EMP
SCOTT                          IDX_JOB_MGR                    NORMAL                      EMP
SCOTT                          IDX_MGR                        NORMAL                      EMP
SCOTT                          PK_EMP                         NORMAL                      EMP

     可见，enable后，相应的索引被重新创建，如果设置10046跟踪事件，也可以从跟踪文件中看到索引被删除的过程。

2.如果创建主键时，已经创建了唯一索引，测试如下：

SQL> create unique index idx_test on test(empno);
 
Index created.
 
SQL> alter table test add constraint pk_test primary key(empno);
 
Table altered.
 
SQL> alter table test modify constraint pk_test disable;
 
Table altered.
 
SQL> select index_name,index_type,table_name from user_indexes where table_name='TEST';
 
no rows selected
 

这种情况下，如果禁用了主键约束，则相应的唯一索引仍然将被删除