实验5：查询当前用户的所有表和视图

SQL> conn scott/scott

已连接。

SQL> select * from tab;

TNAME                               TABTYPE  CLUSTERID                              

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

DEPT                                    TABLE                                           

EMP                                      TABLE                                           

BONUS                                 TABLE                                           

SALGRADE                            TABLE                                                                                                                   

已选择4行。

显示当前用户的所有表和视图。tab是数据字典。

 

SQL> select * from dept;

    DEPTNO DNAME          LOC                                                  

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

        -3                                                                     

        10 ACCOUNTING     NEW YORK                                             

        20 RESEARCH         DALLAS                                               

        30 SALES               CHICAGO                                              

        40 OPERATIONS      BOSTON                                               

SQL> select * from emp;

     EMPNO ENAME      JOB              MGR HIREDATE              SAL       COMM     DEPTNO

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

      7369 SMITH      CLERK           7902 17-12月-80            800                          20

      7499 ALLEN      SALESMAN     7698 20-2月 -81           1600        300            30  

      7521 WARD      SALESMAN     7698 22-2月 -81           1250        500            30                                                                    

      7566 JONES      MANAGER      7839 02-4月 -81           2975                          20                                                                     

      7654 MARTIN     SALESMAN    7698 28-9月 -81           1250       1400            30

      7698 BLAKE      MANAGER      7839 01-5月 -81           2850                          30                                                                    

      7782 CLARK      MANAGER      7839 09-6月 -81           2450                          10                                                                     

      7839 KING       PRESIDENT             17-11月-81            5000                         10                                                                     

      7844 TURNER     SALESMAN    7698 08-9月 -81            1500             0          30                                                         

      7900 JAMES      CLERK           7698 03-12月-81            950                          30

      7902 FORD       ANALYST        7566 03-12月-81           3000                         20

      7934 MILLER     CLERK           7782 23-1月 -82           1300                          10

已选择12行。

*代表所有的列。

 

查看emp的表结构

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)

 

书写SQL语句的原则

• 大小写不敏感，但单、双引号内的大小写敏感
• 关键字不能缩写
• 可以跨行，关键字不能跨行，单引号内不能跨行
• 一般每个字句一行
• 可以排版增加可读性
• 字符串用单引号
• 列的别名用双引

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