演示从表中的行选择第N大/小的值

本文内容

• 软件环境
• Oracle SCOTT 用户
• 从表选择第N大的值
• 从表选择第N小的值

软件环境

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• Windows Server 2008 R2
• Oracle 11g Release 1 (11.1)

Oracle SCOTT 用户

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本文使用 SCOTT 用户的 EMP 表。内容如下：

SQL> select empno,ename,sal
  2  from emp
  3  order by sal desc;

     EMPNO ENAME             SAL
---------- ---------- ----------
      7839 KING             5000
      7902 FORD             3000
      7788 SCOTT            3000
      7566 JONES            2975
      7698 BLAKE            2850
      7782 CLARK            2450
      7499 ALLEN            1600
      7844 TURNER           1500
      7934 MILLER           1300
      7521 WARD             1250
      7654 MARTIN           1250

     EMPNO ENAME             SAL
---------- ---------- ----------
      7876 ADAMS            1100
      7900 JAMES             950
      7369 SMITH             800

已选择14行。

SQL>

从表选择第N大的值

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SQL> select level, max(sal)
  2    from emp
  3   where level = '&n'
  4  connect by prior sal > sal
  5   group by level;
输入 n 的值:  1
原值    3:  where level = '&n'
新值    3:  where level = '1'

     LEVEL   MAX(SAL)
---------- ----------
         1       5000

SQL> select level, max(sal)
  2    from emp
  3   where level = '&n'
  4  connect by prior sal > sal
  5   group by level;
输入 n 的值:  3
原值    3:  where level = '&n'
新值    3:  where level = '3'

     LEVEL   MAX(SAL)
---------- ----------
         3       2975

SQL>

从表选择第N小的值

---

SQL> select level, min(sal)
  2    from emp
  3   where level = '&n'
  4  connect by prior sal < sal
  5   group by level;
输入 n 的值:  1
原值    3:  where level = '&n'
新值    3:  where level = '1'

     LEVEL   MIN(SAL)
---------- ----------
         1        800

SQL> select level, min(sal)
  2    from emp
  3   where level = '&n'
  4  connect by prior sal < sal
  5   group by level;
输入 n 的值:  5
原值    3:  where level = '&n'
新值    3:  where level = '5'

     LEVEL   MIN(SAL)
---------- ----------
         5       1300

SQL>