Oracle SQL 内置函数大全（三）

61.MAX(DISTINCT|ALL)
求最大值,ALL表示对所有的值求最大值,DISTINCT表示对不同的值求最大值,相同的只取一次
SQL> Select Max(Distinct Sal) From Scott.Emp;
MAX(DISTINCTSAL)
----------------
            5000


62.MIN(DISTINCT|ALL)
求最小值,ALL表示对所有的值求最小值,DISTINCT表示对不同的值求最小值,相同的只取一次
SQL> Select Min(All Sal) From Gao.Table3;

MIN(ALLSAL)
-----------
    1111.11


63.STDDEV(Distinct|All)
求标准差,ALL表示对所有的值求标准差,DISTINCT表示只对不同的值求标准差
SQL> Select Stddev(Sal) From Scott.Emp;

STDDEV(SAL)
-----------
  1182.5032

SQL> Select Stddev(Distinct Sal) From Scott.Emp;

STDDEV(DISTINCTSAL)
-------------------
           1229.951

 

64.VARIANCE(DISTINCT|ALL)
求协方差

SQL> Select Variance(Sal) From Scott.Emp;

VARIANCE(SAL)
-------------
    1398313.9


65.GROUP BY
主要用来对一组数进行统计
SQL> Select Deptno,Count(*),Sum(Sal) From Scott.Emp Group By Deptno;

   DEPTNO  COUNT(*)  SUM(SAL)
--------- --------- ---------
       10         3      8750
       20         5     10875
       30         6      9400

 

66.HAVING
对分组统计再加限制条件
SQL> Select Deptno,Count(*),Sum(Sal) From Scott.Emp Group By Deptno Having Nt(*)>=5;

   DEPTNO  COUNT(*)  SUM(SAL)
--------- --------- ---------
       20         5     10875
       30         6      9400
SQL> Select Deptno,Count(*),Sum(Sal) From Scott.Emp Having Count(*)>=5 Group By Tno ;

   DEPTNO  COUNT(*)  SUM(SAL)
--------- --------- ---------
       20         5     10875
       30         6      9400


67.ORDER BY
用于对查询到的结果进行排序输出
SQL> Select Deptno,Ename,Sal From Scott.Emp Order By Deptno,Sal Desc;

   DEPTNO ENAME            SAL
--------- ---------- ---------
       10 KING            5000
       10 CLARK           2450
       10 MILLER          1300
       20 SCOTT           3000
       20 FORD            3000
       20 JONES           2975
       20 ADAMS           1100
       20 SMITH            800
       30 BLAKE           2850
       30 ALLEN           1600
       30 TURNER          1500
       30 WARD            1250
       30 MARTIN          1250
       30 JAMES            950