Question

我正在尝试计算相对日期范围内的值的最大值。假设我有这些列：日期，周，类别，价值。注意：“周”列是相应日期的星期一。

我想生成一个表格，在每个日期，星期，类别组合的最后两周内给出MAX值，以便输出产生以下内容：Date，Week，Category，Value，2WeeksPriorMAX。

我将如何编写该查询？我认为以下方法不起作用：

SELECT Date, Week, Value, 
       MAX(Value) OVER (PARTITION BY Category 
                         ORDER BY Week 
                         ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) as 2WeeksPriorMAX

上述查询未考虑过去2周内给定类别，周组合缺失值的情况，因此在分析前两行时，它将超过2周。

Answer 1

左连接或使用横向连接/子查询可能很昂贵。您可以使用窗口函数执行此操作，但您需要更多逻辑：

select t.*,
       (case when lag(date, 1) over (partition by category order by date) < date - interval '2 week'
             then value
             when lag(date, 2) over (partition by category order by date) < date - interval '2 week'
             then max(value) over (partition by category order by date rows between 1 preceding and current row)
             else max(value) over (partition by category order by date rows between 2 preceding and current row)
        end) as TwoWeekMax
from t;

在相对日期范围内计算MAX值

1 个答案: