一、構建測試表
-- 創建表
create table temp_cwh_test
(
date_time date,
cnt number
);
-- 插入測試數據
insert into temp_cwh_test values (to_date('2019-01-05','yyyy-mm-dd'), 25);
insert into temp_cwh_test values (to_date('2019-02-05','yyyy-mm-dd'), 20);
insert into temp_cwh_test values (to_date('2019-03-05','yyyy-mm-dd'), 63);
insert into temp_cwh_test values (to_date('2019-04-05','yyyy-mm-dd'), 96);
insert into temp_cwh_test values (to_date('2019-05-05','yyyy-mm-dd'), 25);
insert into temp_cwh_test values (to_date('2019-07-05','yyyy-mm-dd'), 12);
insert into temp_cwh_test values (to_date('2019-08-05','yyyy-mm-dd'), 39);
insert into temp_cwh_test values (to_date('2019-09-05','yyyy-mm-dd'), 250);
insert into temp_cwh_test values (to_date('2019-11-05','yyyy-mm-dd'), 1);
insert into temp_cwh_test values (to_date('2019-12-05','yyyy-mm-dd'), 525);
二、環比計算
- 概念
環比 = （第n月 - 第n-1月）/ 第n-1月 * 100%
同比 = （今年第n月 - 去年第n月）/ 去年第n月 * 100%
- 計算
因部分數據缺失，某些月份沒有數據，此時可以構造一個基礎表。
select '2019-' || lpad(rownum, 2, '0') as col from dual connect by level <= 12;
/*
2019-01
2019-02
2019-03
2019-04
2019-05
2019-06
2019-07
2019-08
2019-09
2019-10
2019-11
2019-12
*/
再進行左關聯即可。
使用 lag 窗口函數進行數據偏移，即可計算。
select date_time,
cnt,
cnt_lag,
cnt_diff,
case when (round((case when cnt = 0 then null
else cnt_diff/decode(cnt_lag, 0, 1, cnt_lag) end ) * 100, 2) is
|| '%' as rate
from
(
select a.date_time,
nvl(b.cnt, 0) as cnt,
lag(nvl(b.cnt, 0), 1) over ( order by a.date_time) as cnt_lag,
nvl(b.cnt, 0) - lag(nvl(b.cnt, 0), 1) over ( order by a.date_time) as cnt_diff
from
(
select '2019-' || lpad(rownum, 2, '0') as date_time
from dual
connect by level <= 12
) a
left join temp_cwh_test b
on a.date_time = to_char(b.date_time,'yyyy-mm')
order by a.date_time
) d
order by date_time
/*
1 2019-01 25
2 2019-02 20 25 -5 -20
3 2019-03 63 20 43 215
4 2019-04 96 63 33 52.38
5 2019-05 25 96 -71 -73.96
6 2019-06 0 25 -25
7 2019-07 12 0 12 1200
8 2019-08 39 12 27 225
9 2019-09 250 39 211 541.03
10 2019-10 0 250 -250
11 2019-11 1 0 1 100
12 2019-12 525 1 524 52400
*/
參考鏈接：Oracle計算環比示例