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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;
</span>
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