计算不同行和列的值的差值

Question

请帮助我解决以下问题。 假设我有一个表名为 Data 3 行：Date1、Date2 和访问窗口。我需要计算访问窗口值。它应该是日期1的第(n+1)行和日期2的第n行的差。例如：Date1 的第 2 行值与 date2 值的第 1 行值之差除以 7。请帮助。

Table: Data
------------
Date1           Date2           VW
13-DEC-2011     15-DEC-2011     ?   
18-DEC-2011     16-DEC-2011     ?
21-DEC-2011     24-DEC-2011     ?

谢谢

Answer 1

select
  Date1, 
  Date2,
  lead(Date1) over (order by Date1) next_date1,
  ((lead(Date1) over (order by Date1)) - Date2)/7 as Diff
From DATA_TABLE

对于最后一行你不会得到任何 VW，因为没有 n+1 Date1。

lead(column) 函数从over 子句中指定的下一行返回column 参数的值。

您可以找到示例和其他类似功能here。

UPDATE（回复问题评论 - 如何与另一列进行比较）

select 
  Date1,
  Date2,
  Diff,
  another_column,
  CASE 
    when Diff < another_column then 'it is lower'
    when Diff > another_column then 'it is higher'
    when Diff = another_column then 'are equal'
  END as comparation,
  CASE
    when round(diff -another_column,3) = 0 then 'almost equal'
    else 'definitely not equal'
  END as rounded_comparation
from(
    select
      Date1, 
      Date2,
      lead(Date1) over (order by Date1) next_date1,
      ((lead(Date1) over (order by Date1)) - Date2)/7 as Diff,
      another_column
    From DATA_TABLE
)