SQL> desc emp 名称                                                                                    是否为空? 类型 ----------------------------------------------------------------------------------------- -------- ------------------------------------------------------------ EMPNO											   NOT NULL NUMBER(4) ENAME												    VARCHAR2(10) JOB												    VARCHAR2(9) MGR												    NUMBER(4) HIREDATE											    DATE SAL												    NUMBER(7,2) COMM												    NUMBER(7,2) DEPTNO 											    NUMBER(2)SQL> variable empno number;  SQL> exec :empno:=7844;PL/SQL 过程已成功完成。SQL> select * from emp where empno = :empno;      EMPNO ENAME			  JOB				     MGR HIREDATE	     SAL       COMM	DEPTNO---------- ------------------------------ --------------------------- ---------- ------------ ---------- ---------- ----------      7844 TURNER                         SALESMAN                          7698 08-9月 -81         1500                    30