SQL:define和verify命令及替换变量&

=================替换变量&===============
使用一个&符号来指定一个变量值，执行SQL语句时，会提示用户输入一个数值。

SQL> select sal from emp where empno=&emp_no;

输入 emp_no 的值: 7369



SAL

----------

800



SQL> select * from emp where &conditions;

输入 conditions 的值: sal>2000



EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 20

7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30

7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10

7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20

7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10

7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 20



已选择6行。



SQL> select empno,&column_name, sal from emp where &condition order by &order_by_colunm;

输入 column_name 的值: ename

输入 condition 的值: sal>2000

输入 order_by_colunm 的值: sal desc



EMPNO ENAME SAL

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

7839 KING 5000

7902 FORD 3000

7788 SCOTT 3000

7566 JONES 2975

7698 BLAKE 2850

7782 CLARK 2450



已选择6行。

==================&&========================
&&表示每次重复上一次使用的变量值，第二次执行SQL语句时，不会提示用户输入变量值。

SQL> select * from emp where &&condition;

输入 condition 的值: sal>2000



EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 20

7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30

7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10

7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20

7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10

7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 20



已选择6行。



SQL> select * from emp where &&condition;



EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7566 JONES MANAGER 7839 1981-04-02 00:00:00 2975 20

7698 BLAKE MANAGER 7839 1981-05-01 00:00:00 2850 30

7782 CLARK MANAGER 7839 1981-06-09 00:00:00 2450 10

7788 SCOTT ANALYST 7566 1987-04-19 00:00:00 3000 20

7839 KING PRESIDENT 1981-11-17 00:00:00 5000 10

7902 FORD ANALYST 7566 1981-12-03 00:00:00 3000 20



已选择6行。

============DEFINE和UNDEFINE========================
使用define命令创建和分配一个变量的值。使用undefine命令来删除一个变量。

SQL> define employee_number=7369;

SQL> select * from emp where empno=&employee_number;



EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20



SQL> undefine employee_number;

SQL> select * from emp where empno=&employee_number;

输入 employee_number 的值: 7369



EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20



SQL>

======================VERIFY=================
使用verify命令来显示替换变量之前和之后的值。

SQL> set verify on;

SQL> select * from emp where empno=&employee_number;

输入 employee_number 的值: 7369

原值 1: select * from emp where empno=&employee_number

新值 1: select * from emp where empno=7369



EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO

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

7369 SMITH CLERK 7902 1980-12-17 00:00:00 800 20



SQL>