带有 case when 和 group by 的值列的计数

Question

桌子：

Date            Id       Value                    
2019-02-09      a1       ab            
2019-01-12      a2       cd
2019-12-12      a1       ab
2017-07-23      a1       ab
2018-12-09      a1       ab
2018-12-28      a1       cd
2016-11-09      a2       cd
2016-05-19      a2       ab

输出：

      Id        Max-Min               
      a1        1     
      a2       -1   

目的是创造Max_year_count-Min_year_count per Id.
例如，计算Value column：
(count of occurrence of value in max_year with group by Id)-(count of occurrence of value in min_year with group by Id)
谢谢！！

Answer 1

Oracle 支持FIRST/LAST用于聚合：

SELECT id,
    -- latest year's count
    Count(*) KEEP (Dense_Rank LAST  ORDER BY Extract(YEAR From "Date"))
     -- oldest year's count
  - Count(*) KEEP (Dense_Rank FIRST ORDER BY Extract(YEAR From "Date"))
FROM DATA
GROUP BY Id