用上一行的值减去最近一行的值（第 -1 天）

Question

我有一个 table 每天都有增量值。我想用前一行的值减去最近一行的值 (day -1)

例如，这将是完美的：

SUM(value) OVER (PARTITION BY item_name ORDER BY date ROWS BETWEEN 1 PRECEDING AND CURRENT ROW)

但是，我需要应用 DIFF 函数而不是 SUM 函数。

Answer 1

只需使用lag():

select val - lag(val) over (partition by item_name order by date)

Subtract the value of the most recent row with the value of the previous row (day -1)