sqlplus中单&与双&&的区别

在单&的情况中，每次执行sql，oracle都要提示用户输入值，然后执行，在双&中，只需用户输入一次值，以后的每次运行都会使用第一次输入的值

SQL> select * from employees where employee_id=&id;

输入 id 的值:  205

原值    1: select * from employees where employee_id=&id

新值    1: select * from employees where employee_id=205

EMPLOYEE_ID FIRST_NAME

----------- ----------------------------------------

LAST_NAME

--------------------------------------------------

EMAIL

--------------------------------------------------

PHONE_NUMBER                             HIRE_DATE      JOB_ID

---------------------------------------- -------------- --------------------

    SALARY COMMISSION_PCT MANAGER_ID DEPARTMENT_ID

---------- -------------- ---------- -------------

        205 Shelley

Higgins

SHIGGINS

EMPLOYEE_ID FIRST_NAME

----------- ----------------------------------------

LAST_NAME

--------------------------------------------------

EMAIL

--------------------------------------------------

PHONE_NUMBER                             HIRE_DATE      JOB_ID

---------------------------------------- -------------- --------------------

    SALARY COMMISSION_PCT MANAGER_ID DEPARTMENT_ID

---------- -------------- ---------- -------------

515.123.8080                             07-6月 -02     AC_MGR

     12008                       101           110

SQL> select * from employees where employee_id=&id;

输入 id 的值:  206

原值    1: select * from employees where employee_id=&id

新值    1: select * from employees where employee_id=206

EMPLOYEE_ID FIRST_NAME

----------- ----------------------------------------

LAST_NAME

--------------------------------------------------

EMAIL

--------------------------------------------------

PHONE_NUMBER                             HIRE_DATE      JOB_ID

---------------------------------------- -------------- --------------------

    SALARY COMMISSION_PCT MANAGER_ID DEPARTMENT_ID

---------- -------------- ---------- -------------

        206 William

Gietz

WGIETZ

EMPLOYEE_ID FIRST_NAME

----------- ----------------------------------------

LAST_NAME

--------------------------------------------------

EMAIL

--------------------------------------------------

PHONE_NUMBER                             HIRE_DATE      JOB_ID

---------------------------------------- -------------- --------------------

    SALARY COMMISSION_PCT MANAGER_ID DEPARTMENT_ID

---------- -------------- ---------- -------------

515.123.8181                             07-6月 -02     AC_ACCOUNT

      8300                       205           110

SQL> select * from employees where employee_id=&&id;

输入 id 的值:  207

原值    1: select * from employees where employee_id=&&id

新值    1: select * from employees where employee_id=207

未选定行

SQL> select * from employees where employee_id=&&id;

原值    1: select * from employees where employee_id=&&id

新值    1: select * from employees where employee_id=207

未选定行

SQL> select * from employees where employee_id=&&id;

原值    1: select * from employees where employee_id=&&id

新值    1: select * from employees where employee_id=207

未选定行

SQL>