oracle实验1-3:简单的查询语句

 第一部分 sql基础

 select语句的作用

  • 查询指定的行
  • 查询指定的列
  • 多张表的联合查询

   select子句指定要查询的列,from字句指定要查询的表。

实验1:查询一张表的所有行和所有列

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。

实验2:查询一张表的所有行,列的顺序我们自己决定

SQL> select ename,sal from emp;

ENAME             SAL                                                          
---------- ----------                                                          
SMITH             800                                                          
ALLEN            1600                                                          
WARD            1250                                                          
JONES            2975                                                          
MARTIN          1250                                                          
BLAKE            2850                                                          
CLARK            2450                                                          
KING              5000                                                          
TURNER          1500                                                          
JAMES              950                                                          
FORD             3000                                                                                                                  
MILLER           1300                                                          

已选择12行。

实验3:查询表的某些列,在列上使用表达式

SQL> select ename,sal,sal+3000 from emp;

ENAME             SAL   SAL+3000                                               
---------- ---------- ----------                                               
SMITH             800         3800                                               
ALLEN            1600        4600                                               
WARD             1250       4250                                               
JONES            2975        5975                                               
MARTIN           1250       4250                                               
BLAKE            2850        5850                                               
CLARK            2450        5450                                               
KING             5000         8000                                               
TURNER           1500       4500                                               
JAMES             950         3950                                               
FORD             3000        6000                                                                                             
MILLER           1300        4300                                               

已选择12行。

表达式有优先级,先乘除,后加减,括号强制优先级。

SQL> select ename,sal,12*sal+300 from emp;

ENAME             SAL 12*SAL+300                                               
---------- ---------- -------------                                              
SMITH              800          9900                                               
ALLEN            1600        19500                                               
WARD            1250        15300                                               
JONES            2975        36000                                               
MARTIN          1250        15300                                               
BLAKE            2850        34500                                               
CLARK            2450        29700                                               
KING              5000        60300                                               
TURNER          1500        18300                                               
JAMES             950         11700                                               
FORD             3000        36300                                                                                               
MILLER           1300        15900                                               

已选择12行。

SQL> select ename,sal,12*(sal+300) from emp;

ENAME             SAL 12*(SAL+300)                                             
---------- ---------- ------------                                             
SMITH             800         13200                                             
ALLEN            1600        22800                                             
WARD            1250        18600                                             
JONES            2975        39300                                             
MARTIN          1250        18600                                             
BLAKE           2850         37800                                             
CLARK           2450         33000                                             
KING             5000         63600                                             
TURNER         1500         21600                                             
JAMES             950         15000                                             
FORD             3000        39600                                                                                          
MILLER           1300        19200                                             

已选择12行。

 

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posted on 2013-06-16 20:41  不吃鱼的小胖猫  阅读(489)  评论(0编辑  收藏  举报