Question

I have two tables, namely Price List (Table A) and Order Record (Table B)

Table A

SKU Offer Date  Amt
AAA 20120115    22
AAA 20120223    24
AAA 20120331    25
AAA 20120520    28

Table B

Customer   SKU  Order Date
A001       AAA  20120201
B001       AAA  20120410
C001       AAA  20120531

I have to retrieve the correct pricing for each customer based on the order date. The expected output should be like this:-

Customer  SKU   Order Date  Amt
A001      AAA   20120201    22
B001      AAA   20120410    25
C001      AAA   20120531    28

Thanks.

Answer 1

A left join (or NOT EXISTS subquery) can be used to ensure that the join between the two tables uses the “most recent” row from the prices table that is dated on or before the order date. I assume that’s the relationship between the tables that you want to achieve:

Setup:

create table Prices (
    SKU char(3) not null,
    OfferDate date not null,
    Amt int not null
)
go
insert into Prices (SKU, OfferDate,  Amt) values
('AAA','20120115',    22),
('AAA','20120223',    24),
('AAA','20120331',    25),
('AAA','20120520',    28)
go
create table Orders (
    Customer char(4) not null,
    SKU char(3) not null,
    OrderDate date not null
)
go
insert into Orders (Customer,   SKU,  OrderDate) values
('A001','AAA','20120201'),
('B001','AAA','20120410'),
('C001','AAA','20120531')
go

Query:

select
    o.*, /* TODO - Explicit columns */
    p.Amt
from
    Orders o
        inner join
    Prices p
        on
            o.SKU = p.SKU and
            o.OrderDate >= p.OfferDate
        left join
    Prices p_later
        on
            o.SKU = p_later.SKU and
            o.OrderDate >= p_later.OfferDate and
            p_later.OfferDate > p.OfferDate 
where
    p_later.SKU is null