sql lag函数

lag

https://spark.apache.org/docs/latest/api/sql/#lag
lag(input[, offset[, default]]) OVER (PARTITION BY a ORDER BY b)
input - 求lag的目标字段
offset - lag步数
default - 空值用什么填充

select *,
lag(`fa_adjust`,-2, 0) over (partition by (`stock_id`, `sku`) order by `date` desc) `lag1_fa`, 
lag(`fa_adjust`,-3, 0) over (partition by (`stock_id`, `sku`) order by `date` desc) `lag2_fa`, 
lag(`fa_adjust`,-4, 0) over (partition by (`stock_id`, `sku`) order by `date` desc) `lag3_fa`
from input1