sql系列(基础篇)-第二章约束和排序数据

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第二章 约束和排序数据

1. 在 emp 表中选择工资介于 1500 到 2500 的员工的信息;
注意:使用 between 下边界 and 上边界时,条件包括边界值;

SCOTT@ORCL>l       
  1  select * from emp
  2* where sal between 1500 and 2500
SCOTT@ORCL>/

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30

2. 在emp表中选择位于20,30 部门的员工的信息;

SCOTT@ORCL>select *from emp
  2  where deptno in (20,30);

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20

11 rows selected.

3. 在emp表中选择位于员工的名字中包含大写字符 ‘A’ 的员工的信息;

SCOTT@ORCL>select * from emp
  2  where ename like '%A%';

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30

7 rows selected.
	
注意:如果查询的名字中包含%或者_ ,而且查询的时候又要查询这样的信息,需要用到换位码。
注意:通配符%,表示0或者多个字符一样;通配符_,表示1个字符一样;

	3.1 创建与 emp 表结构相同的表;
SCOTT@ORCL>create table emp_n                    /* 参照emp表创建新表emp_n */
  2  as select * from emp where 1=2;           /* 加where 1=2 一致表结构没有数据 */

Table created.

SCOTT@ORCL>select * from emp_n;

no rows selected

	3.2 添加包含通配符的测试用数据;
SCOTT@ORCL>insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal);
Enter value for empno: 1001
Enter value for ename: 'whwh%gogo'
Enter value for sal: 1000
old   1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new   1: insert into emp_n(empno,ename,sal) values(1001,'whwh%gogo',1000)

1 row created.

SCOTT@ORCL>/
Enter value for empno: 1002
Enter value for ename: '%whwh'
Enter value for sal: 2000
old   1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new   1: insert into emp_n(empno,ename,sal) values(1002,'%whwh',2000)

1 row created.

SCOTT@ORCL>/
Enter value for empno: 1003
Enter value for ename: 'whwh_gogo'
Enter value for sal: 3000
old   1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new   1: insert into emp_n(empno,ename,sal) values(1003,'whwh_gogo',3000)

1 row created.

SCOTT@ORCL>/
Enter value for empno: 1004
Enter value for ename: '_gogo'
Enter value for sal: 4000
old   1: insert into emp_n(empno,ename,sal) values(&empno,&ename,&sal)
new   1: insert into emp_n(empno,ename,sal) values(1004,'_gogo',4000)

1 row created.

SCOTT@ORCL>commit;

Commit complete.

SCOTT@ORCL>select * from emp_n;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      1001 whwh%gogo                                       1000
      1002 %whwh                                           2000
      1003 whwh_gogo                                       3000
      1004 _gogo                                           4000

	3.3 换位码的使用方法;(此处以\作为换位码,换位码还可以指定其他字符)
例:检索包含%的记录信息;
SCOTT@ORCL>select * from emp_n
  2  where ename like '%\%%' escape '\';

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      1001 whwh%gogo                                       1000
      1002 %whwh                                           2000

SCOTT@ORCL>select * from emp_n
  2  where ename like '%\%%';

no rows selected

例:检索以%开头的记录信息;
SCOTT@ORCL>select * from emp_n
  2  where ename like '\%%' escape '\';

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      1002 %whwh                                           2000

例:检索包含_的记录信息;
SCOTT@ORCL>select * from emp_n
  2  where ename like '%\_%' escape '\';

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      1003 whwh_gogo                                       3000
      1004 _gogo                                           4000

例:检索以_开头的记录信息;
SCOTT@ORCL>select * from emp_n
  2  where ename like '\_%' escape '\';

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      1004 _gogo                                           4000

4 复合条件的使用
	4.1 对于and条件的复合(可以将between...and...进行转换)
	
例:在emp表中选择工资介于2000到3000的员工的信息;
SCOTT@ORCL>select * from emp
  2  where sal>=2000 and sal<=3000;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20

SCOTT@ORCL>select * from emp
  2  where sal between 2000 and 3000;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20

	4.2 对于or条件复合(可以将in()进行转换)
例:在emp表中选择10号和20号部门的员工信息;
SCOTT@ORCL>select * from emp
  2  where deptno=10 or deptno=20;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

8 rows selected.

SCOTT@ORCL>select * from emp
  2  where deptno in (10,20);

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

8 rows selected.

	5 对于表中数据的排序
	5.1 asc  表示按照所给字段进行升序排列(默认升序)
		desc 表示按照所给字段进行降序排列
例:将emp表中10号部门的员工信息按照sal列升序排列
SCOTT@ORCL>select * from emp 
  2  where deptno=10;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

SCOTT@ORCL>select * from emp
  2  where deptno=10
  3  order by sal asc;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7839 KING       PRESIDENT            17-NOV-81       5000                    10

SCOTT@ORCL>select * from emp
  2  where deptno=10
  3  order by sal;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7839 KING       PRESIDENT            17-NOV-81       5000                    10

例:将emp表中20号部门的员工信息按照sal列降序排列
SCOTT@ORCL>select * from emp
  2  where deptno=20
  3  order by sal desc;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20

	5.2 如果order by 后面跟多个字段,则将结果集先按照第1个字段进行排序【条件1】,
		再按第2个字段进行排序【条件2】;
	注意:【条件1】如果按照第1个字段分不开先后顺序的时候,才会按照第2个字段排序;
		   asc 或者desc 影响的字段,仅仅是它紧挨着的那个字段;
例:将emp表中10号部门的员工信息按sal降序排列,empno升序排列;
SCOTT@ORCL>select * from emp
  2  where deptno=10
  3  order by sal desc,empno asc;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

例:将emp表中20号部门的员工信息按照empno 降序排列,sal升序排列;
SCOTT@ORCL>select * from emp
  2  where deptno=20
  3  order by empno desc,sal asc;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20

	 5.3 除了可以使用字段排序,还可以使用字段所在的先后位置排序;
确定字段在表中的先后顺序;
SCOTT@ORCL>set lines 100
SCOTT@ORCL>desc emp;
 Name                                                  Null?    Type
 ----------------------------------------------------- -------- ------------------------------------
 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)

 例:将emp表中10号部门的员工信息按sal降序排列,empno升序排列;
 SCOTT@ORCL>select * from emp
  2  where deptno=10
  3  order by 6 desc,1 asc;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10

例:将emp表中20号部门的员工信息按照empno 降序排列,sal升序排列;
SCOTT@ORCL>select * from emp
  2  where deptno=20
  3  order by 1 desc,6 asc;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20

	 5.4 除了可以使用number 类型的字段进行排序外,还可以使用字符串或者时间类型的字段进行排序;
	 注意:字符串排序:按照字符对应的ASCII码的先后进行排序;
	       日期排序:按照日期的先后进行排序,时间越往后越大;
例:将emp表中员工按照job升序、ename降序进行排列;(先按Job排序,同样的job按ename降序)
SCOTT@ORCL>select * from emp
  2  order by job asc,ename desc;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7788 SCOTT      ANALYST         7566 19-APR-87       3000                    20
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7876 ADAMS      CLERK           7788 23-MAY-87       1100                    20
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30

14 rows selected.

例:将emp表中员工按照 HIREDATE 升序,sal降序排列(如果HIREDATE相同,按照sal降序)
先将HIREDATE显示格式设定
SCOTT@ORCL>alter session set nls_date_format='yyyy-mm-dd';

Session altered.

SCOTT@ORCL>select * from emp
  2  order by hiredate asc,sal desc;

     EMPNO ENAME      JOB              MGR HIREDATE          SAL       COMM     DEPTNO
---------- ---------- --------- ---------- ---------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 1980-12-17        800                    20
      7499 ALLEN      SALESMAN        7698 1981-02-20       1600        300         30
      7521 WARD       SALESMAN        7698 1981-02-22       1250        500         30
      7566 JONES      MANAGER         7839 1981-04-02       2975                    20
      7698 BLAKE      MANAGER         7839 1981-05-01       2850                    30
      7782 CLARK      MANAGER         7839 1981-06-09       2450                    10
      7844 TURNER     SALESMAN        7698 1981-09-08       1500          0         30
      7654 MARTIN     SALESMAN        7698 1981-09-28       1250       1400         30
      7839 KING       PRESIDENT            1981-11-17       5000                    10
      7902 FORD       ANALYST         7566 1981-12-03       3000                    20
      7900 JAMES      CLERK           7698 1981-12-03        950                    30
      7934 MILLER     CLERK           7782 1982-01-23       1300                    10
      7788 SCOTT      ANALYST         7566 1987-04-19       3000                    20
      7876 ADAMS      CLERK           7788 1987-05-23       1100                    20

14 rows selected.

	6. 使用结果集中的别名进行排序;
例:按照emp表中员工对于的年薪(sal*12)进行排序;
SCOTT@ORCL>select empno,ename,hiredate,sal*12 year_sal
  2  from emp
  3  order by year_sal desc;

     EMPNO ENAME      HIREDATE     YEAR_SAL
---------- ---------- ---------- ----------
      7839 KING       1981-11-17      60000
      7902 FORD       1981-12-03      36000
      7788 SCOTT      1987-04-19      36000
      7566 JONES      1981-04-02      35700
      7698 BLAKE      1981-05-01      34200
      7782 CLARK      1981-06-09      29400
      7499 ALLEN      1981-02-20      19200
      7844 TURNER     1981-09-08      18000
      7934 MILLER     1982-01-23      15600
      7521 WARD       1981-02-22      15000
      7654 MARTIN     1981-09-28      15000
      7876 ADAMS      1987-05-23      13200
      7900 JAMES      1981-12-03      11400
      7369 SMITH      1980-12-17       9600

14 rows selected.

注意:当然也可以按照字符串、日期对应的别名进行排序;

	7. 如果排序的字段中包含null值,结果会怎么样?
	注意:在字段进行比较大小的时候,null 值比任何值都大;
例:emp表中员工的信息按照comm降序排列;
SCOTT@ORCL>select * from emp
  2  order by comm desc;

     EMPNO ENAME      JOB              MGR HIREDATE          SAL       COMM     DEPTNO
---------- ---------- --------- ---------- ---------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 1980-12-17        800                    20
      7782 CLARK      MANAGER         7839 1981-06-09       2450                    10
      7902 FORD       ANALYST         7566 1981-12-03       3000                    20
      7900 JAMES      CLERK           7698 1981-12-03        950                    30
      7876 ADAMS      CLERK           7788 1987-05-23       1100                    20
      7566 JONES      MANAGER         7839 1981-04-02       2975                    20
      7698 BLAKE      MANAGER         7839 1981-05-01       2850                    30
      7934 MILLER     CLERK           7782 1982-01-23       1300                    10
      7788 SCOTT      ANALYST         7566 1987-04-19       3000                    20
      7839 KING       PRESIDENT            1981-11-17       5000                    10
      7654 MARTIN     SALESMAN        7698 1981-09-28       1250       1400         30
      7521 WARD       SALESMAN        7698 1981-02-22       1250        500         30
      7499 ALLEN      SALESMAN        7698 1981-02-20       1600        300         30
      7844 TURNER     SALESMAN        7698 1981-09-08       1500          0         30

14 rows selected.

注意:null 值之间的排序不考虑(因为Null 和 null 之间无法比较大小)

如果我想将comm有值的部分换到上面,该怎么办?
SCOTT@ORCL>select * from emp
  2  order by comm desc nulls last;

     EMPNO ENAME      JOB              MGR HIREDATE          SAL       COMM     DEPTNO
---------- ---------- --------- ---------- ---------- ---------- ---------- ----------
      7654 MARTIN     SALESMAN        7698 1981-09-28       1250       1400         30
      7521 WARD       SALESMAN        7698 1981-02-22       1250        500         30
      7499 ALLEN      SALESMAN        7698 1981-02-20       1600        300         30
      7844 TURNER     SALESMAN        7698 1981-09-08       1500          0         30
      7788 SCOTT      ANALYST         7566 1987-04-19       3000                    20
      7839 KING       PRESIDENT            1981-11-17       5000                    10
      7876 ADAMS      CLERK           7788 1987-05-23       1100                    20
      7900 JAMES      CLERK           7698 1981-12-03        950                    30
      7902 FORD       ANALYST         7566 1981-12-03       3000                    20
      7934 MILLER     CLERK           7782 1982-01-23       1300                    10
      7698 BLAKE      MANAGER         7839 1981-05-01       2850                    30
      7566 JONES      MANAGER         7839 1981-04-02       2975                    20
      7369 SMITH      CLERK           7902 1980-12-17        800                    20
      7782 CLARK      MANAGER         7839 1981-06-09       2450                    10

14 rows selected.

同理:自己验证 升序 排列
SCOTT@ORCL>select * from emp
  2  order by comm asc nulls first;






















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