How to Query and Update/Insert Large Tables ...

Question

I have the following 2 tables:
Table 1: Pricing
This table holds pricing details of all Items (roughly 150,000 items). One Item has three types of prices Standard, Promotion, and Discounted. Therefore the table contains roughly 150,000 * 3 records. Also the prices may get updated frequently every day.
Item#---Type------------FromDate---ToDate-----Price
===================================
AAA-----Standard------01/01/05---31/12/05---1.50
AAA-----Promotion----16/12/05---20/12/05---1.40     
AAA-----Discounted---10/12/05---15/12/05---1.20
BBB-----Standard------01/01/05---31/12/05---1.60
BBB-----Promotion----17/12/05---18/12/05---1.30
BBB-----Discounted---10/12/05---15/12/05---1.50
Table 2: BestPrice
At a given date, this table contains the best price (lowest price) of each item for the following 21 days (including the current date). The POS system is accessing this table to get the daily best price for billing customers.
Item#----Date--------BestPrice
=====================
AAA------17/12/05----1.40
AAA------18/12/05----1.40     
AAA------19/12/05----1.40
AAA------20/12/05----1.40
AAA------21/12/05----1.50
BBB------17/12/05----1.30
BBB------18/12/05----1.30
BBB------19/12/05----1.60
BBB------20/12/05----1.60
BBB------21/12/05----1.60
Problem Statement:
Table 2 (BestPrice) needs to get updated from Table 1 (Pricing) at least once every day with the best price for each item for the next 21 days (including the current day). What’s the most efficient method to perform this job?

Answer 1

I don't know really why your application needs to use BestPrice table!
It is not clear what it does for it because querying will not be better than querying the pricing table. This will be very fast with an index on intem#
On the other hand, why do you use three rows per item in Pricing table? it could be one row per item.
Any way, to populate the table for the first time :
insert into bestprice
select item#
     , dte
     , min(price) bestprice
from pricing, (select trunc(sysdate) + rownum - 1 dte from dual connect by rownum <= 21) t
where  dte  between fromdate and todate
group by dte, item#Now, you can have a row trigger (update) on Pricing table which can change BestPrice table according to a change in Pricing tabe.
Then you have to use a daily job that can be based on the following statement:
update BestPrice B
set dte = trunc(sysdate) + 20
  , BestPrice =
         select min(price)
         from Pricing P
         where P.item# = B.item#
            and B.dte between P.FromDate and P.ToDate
where dte = trunc (sysdate) - 1Message was edited by:
Michel SALAIS
I forgot to say that that if your periods in the pricing table don't covere a desired date in the BestPrice table then my insert statement will not treat it and my update will put it to NULL