Oracle 9i 分析函数参考手册(18)

SAMPLE：下例计算1998年每月销售的累积总体和样本变量(本例在SH用户下运行)

SELECT t.calendar_month_desc,
VAR_POP(SUM(s.amount_sold))
OVER (ORDER BY t.calendar_month_desc) "Var_Pop",
VAR_SAMP(SUM(s.amount_sold))
OVER (ORDER BY t.calendar_month_desc) "Var_Samp"
FROM sales s, times t
WHERE s.time_id = t.time_id AND t.calendar_year = 1998
GROUP BY t.calendar_month_desc;

CALENDAR Var_Pop Var_Samp
-------- ---------- ----------
1998-01 0
1998-02 6.1321E+11 1.2264E+12
1998-03 4.7058E+11 7.0587E+11
1998-04 4.6929E+11 6.2572E+11
1998-05 1.5524E+12 1.9405E+12
1998-06 2.3711E+12 2.8453E+12
1998-07 3.7464E+12 4.3708E+12
1998-08 3.7852E+12 4.3260E+12
1998-09 3.5753E+12 4.0222E+12
1998-10 3.4343E+12 3.8159E+12
1998-11 3.4245E+12 3.7669E+12
1998-12 4.8937E+12 5.3386E+12

VAR_SAMP

　　功能描述：(Variance Sample)该函数返回非空集合的样本变量(忽略null)，VAR_POP进行如下计算：

　　(SUM(expr*expr)-SUM(expr)*SUM(expr)/COUNT(expr))/(COUNT(expr)-1)

　　SAMPLE：下例计算1998年每月销售的累积总体和样本变量

SELECT t.calendar_month_desc,
VAR_POP(SUM(s.amount_sold))
OVER (ORDER BY t.calendar_month_desc) "Var_Pop",
VAR_SAMP(SUM(s.amount_sold))
OVER (ORDER BY t.calendar_month_desc) "Var_Samp"
FROM sales s, times t
WHERE s.time_id = t.time_id AND t.calendar_year = 1998
GROUP BY t.calendar_month_desc;

CALENDAR Var_Pop Var_Samp
-------- ---------- ----------
1998-01 0
1998-02 6.1321E+11 1.2264E+12
1998-03 4.7058E+11 7.0587E+11
1998-04 4.6929E+11 6.2572E+11
1998-05 1.5524E+12 1.9405E+12
1998-06 2.3711E+12 2.8453E+12
1998-07 3.7464E+12 4.3708E+12
1998-08 3.7852E+12 4.3260E+12
1998-09 3.5753E+12 4.0222E+12
1998-10 3.4343E+12 3.8159E+12
1998-11 3.4245E+12 3.7669E+12
1998-12 4.8937E+12 5.3386E+12

VARIANCE

　　功能描述：该函数返回表达式的变量，Oracle计算该变量如下：

　　如果表达式中行数为1，则返回0

　　如果表达式中行数大于1，则返回VAR_SAMP

　　SAMPLE：下例返回部门30按雇佣日期排序的薪水值的累积变化

SELECT last_name, salary, VARIANCE(salary)
OVER (ORDER BY hire_date) "Variance"
FROM employees
WHERE department_id = 30;

LAST_NAME SALARY Variance
------------------------- ---------- ----------
Raphaely 11000 0
Khoo 3100 31205000
Tobias 2800 21623333.3
Baida 2900 16283333.3
Himuro 2600 13317000
Colmenares 2500 11307000