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)