Oracle查询-各城市的逐年人口趋势

Question

我从sql查询获得此结果。该表的名称为“人口”，其列为：地区，国家/地区，城市，year_v和人口：

REGION  COUNTRY CITY    YEAR_V  POPULATION
europe  france  paris   2015    2.1
europe  france  paris   2017    2.2
europe  france  lyon    2016    .4
europe  spain   madrid  2012    2.9
europe  spain   madrid  2013    3
europe  spain   madrid  2014    3.1
europe  spain   madrid  2016    .8

我需要从这里得到的是按城市划分的逐年人口趋势，它应该像这样：

city    growth   year_diff
Madrid   0.10    2012-2013
Madrid   0.10    2013-2014
Paris    0.10    2015-2017

对于如何编写可以返回这种结果的查询的提示，我将不胜感激。

Answer 1

您将使用lag()：

select region, country, city,
       year_v, population,
       prev_year_v, prev_population,
       (population - prev_population) as diff
from (select t.*,
             lag(population) over (partition by region, country, city order by year_v) as prev_population,
             lag(year_v) over (partition by region, country, city order by year_v) as prev_year_v,
      from t
     ) t
where prev_year_v is not null;