Nearest date value

问题

I need a solution to find the nearest date value for missing values based on date.Suppose I have a temporary table like below with columns Product Date Value

Product      Date     Value  
  P1         1/10      10  
  P1         2/10      20  
  P1         3/10          
  P1         4/10   

Here you find that for date 3/10 and 4/10 there are no values and it should copy the values from the nearest date that is 2/10 to 3/10 and 4/10 i.e 20. I used the lag function in HANA and it is copying the value only for 3/10 and for date 4/10 it is null. Is there any function in HANA which can take the value from the nearest date value like kind of Repetitive LAG.

I don't want to do cursor and CTEs are not supported in SQL script as far as I know

BR Arshad

回答1:

Could you please check following SQLScript statement for SAP HANA database

select
    Product, Date, Value
from (
select 
    pv.Product,
    pv.Date,
    ifnull(pv.Value, p.Value) as Value,
    row_number() over (partition by pv.Product, pv.Date order by p.Date desc) as rn
from ProductValue pv
left join ProductValue p
    on 
    pv.Value is null and
    p.Product = pv.Product and
    p.Date < pv.Date and
    p.Value is not null
) t
where rn = 1
order by
    Product,
    Date

I used a self-join in combination with ROW_NUMBER() function in WHERE clause

Output of above SAP HANA SQL script is as follows

来源：https://stackoverflow.com/questions/47028803/nearest-date-value