分析函数之窗口函数
分析函数之窗口函数
当统计量随着当前记录变化时，就需要用到窗口函数了
特殊情况： select sum (c1) over() from 加的所有的和；
select sum(c1) over(order by c2) from 与
over ( ORDER BY site_id ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING) 相同
一、对行数规则的结果集，窗口仅涉及行数的移动
1、几种情况
SUM((cnt)) over(ORDER BY site_id
rows BETWEEN UNBOUNDED preceding AND UNBOUNDED following) AS total
行 范围 为 无限向前 无限向后
rows BETWEEN 1 preceding AND n following) AS total
行 范围为 当前行前一行，当前行后n 行
rows BETWEEN 0 preceding AND 0 following) AS total
行 范围为 只统计当前行
rows BETWEEN 1 preceding AND current row) AS total
行 范围为 当前行前一行和本行
2、例子
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (1, 10);
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (2, 4);
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (3, 2);
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (4, 2);
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (5, 4);
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (6, 19);
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (7, 4);
insert into test2 (SITE_ID, SALE_LOTTERY_CNT)
values (8, 19);
a、计算每个销售点销量占所有销量的比例
SELECT site_id,SUM(sale_lottery_cnt), 100*SUM(sale_lottery_cnt)/
SUM(SUM(sale_lottery_cnt)) over(ORDER BY site_id rows BETWEEN UNBOUNDED preceding AND UNBOUNDED following)||'%' AS Percent_
FROM test2
GROUP BY site_id;
1 10 15.625%
2 4 6.25%
3 2 3.125%
4 2 3.125%
5 4 6.25%
6 19 29.6875%
7 4 6.25%
8 19 29.6875%
b、按销售点id排列，计算每个销售点销量、小于等于此销售点号的总销量
SELECT site_id,SUM(sale_lottery_cnt),
SUM(SUM(sale_lottery_cnt)) over(ORDER BY site_id rows BETWEEN UNBOUNDED preceding AND 0 following) AS total
FROM test2
GROUP BY site_id;
1 10 10
2 4 14
3 2 16
4 2 18
5 4 22
6 19 41
7 4 45
8 19 64
二、对行数不规则的结果集，窗口也可根据日期移动
比如求5日内的平均值
avg（c1) over( over by trunc(c2_day) range between interval '2' day preceding and interval '2' day following)