1.列标题和数据的默认显示格式
SQL> alter session 2 set nls_date_language = 'AMERICAN'; Session altered SQL> col hiredate for a15; SQL> col ename for a8;
例：观察不同数据类型的显示方式。
SQL> select * 2 from emp; EMPNO ENAME JOB MGR HIREDATE SAL COMM DEPTNO ----- -------- --------- ----- --------------- --------- --------- ------ 7369 SMITH CLERK 7902 1980-12-17 800.00 20 7499 ALLEN SALESMAN 7698 1981-2-20 1600.00 300.00 30 7521 WARD SALESMAN 7698 1981-2-22 1250.00 500.00 30 7566 JONES MANAGER 7839 1981-4-2 2975.00 20 7654 MARTIN SALESMAN 7698 1981-9-28 1250.00 1400.00 30 7698 BLAKE MANAGER 7839 1981-5-1 2850.00 30 7782 CLARK MANAGER 7839 1981-6-9 2450.00 10 7788 SCOTT ANALYST 7566 1982-12-9 3000.00 20 7839 KING PRESIDENT 1981-11-17 5000.00 10 7844 TURNER SALESMAN 7698 1981-9-8 1500.00 0.00 30 7876 ADAMS CLERK 7788 1983-1-12 1100.00 20 7900 JAMES CLERK 7698 1981-12-3 950.00 30 7902 FORD ANALYST 7566 1981-12-3 3000.00 20 7934 MILLER CLERK 7782 1982-1-23 1300.00 10 1234 ASK MANAGER 1 2009-8-31 10.00 10.00 10 15 rows selected
2.连接操作符
可使用连接符“||”，用于列与列、列与算术表达式或列与常理之间创建一个字符表达式。
任务：将姓名和工作连接作为整体输出SQL> select ename || job as "Employee" 2 from emp; Employee ------------------- SMITHCLERK ALLENSALESMAN WARDSALESMAN JONESMANAGER MARTINSALESMAN BLAKEMANAGER CLARKMANAGER SCOTTANALYST KINGPRESIDENT TURNERSALESMAN ADAMSCLERK JAMESCLERK FORDANALYST MILLERCLERK ASKMANAGER 15 rows selected
3.原义字符串
任务：使用原义字符串"is a"连接ename和job，可增强输出的可读性。SQL> select ename || ' is a ' || job 2 as "Employee Details" 3 from emp; Employee Details ------------------------- SMITH is a CLERK ALLEN is a SALESMAN WARD is a SALESMAN JONES is a MANAGER MARTIN is a SALESMAN BLAKE is a MANAGER CLARK is a MANAGER SCOTT is a ANALYST KING is a PRESIDENT TURNER is a SALESMAN ADAMS is a CLERK JAMES is a CLERK FORD is a ANALYST MILLER is a CLERK ASK is a MANAGER 15 rows selected
4.显示表结构
可以使用describe命令显示一个表的结构。（列名、数据类型以及是否为空）
SQL> describe dept Name Type Nullable Default Comments ------ ------------ -------- ------- -------- DEPTNO NUMBER(2) DNAME VARCHAR2(14) Y LOC VARCHAR2(13) Y
下午难得有时间看看基础知识，内容虽简单，可刚接触Oracle，认真才是实在，实在才是根本！
