如何在SQL中获取以前的日期记录

Question

I am Left joining two tables Table 1 and Table 2 on basis of invoice date & created date and also sales office Table 1 has invoice date , sales office and other columns Table 2 has created date , price and other columns so i want invoice date from table 1 and price from table 2 and for invoice date not present in created date of table 2 , I need price of previous created date from table 2 next to invoice date in output

Table 1

invoice date    sales office 
01-04-2019  ABC 
02-04-2019  ABC 
04-04-2019  ABC 
06-04-2019  ABC 

Table 2

created date    sales office    price
01-04-2019  ABC          10
02-04-2019  ABC          20
05-04-2019  ABC          30
07-04-2019  ABC          30

Output

Invoice date    New date    price
01-04-2019  01-04-2019  10
02-04-2019  02-04-2019  20
04-04-2019  02-04-2019  20
06-04-2019  05-04-2019  30

Answer 1

If you want the most recent price for each invoice, then you can use a lateral join or correlated subquery:

select i.invoicedate, p.createddate, p.price
from invoices i outer apply
     (select top (1) p.*
      from prices p
      where p.salesoffice = i.salesoffice and
            p.createddate <= i.invoicedate
      order by p.createddate desc
     ) p;

In other databases, you can use window functions:

select ip.*
from (select i.invoicedate, p.createddate, p.price,
             row_number() over (partition by i.invoicedate order by p.createddate desc) as seqnum
      from invoices i join
           prices p
           on p.salesoffice = i.salesoffice and
              p.createddate <= i.invoicedate
     ) ip
where seqnum = 1;