What are the pitfalls when storing data retrieved from an api I can get some financial data from our vendor via their API. In this case API is too strong a word. Basically we can get only an array of orders for a given time range. What we paid them for the product, what they charges us for shipping, etc. 

To report on and analyze this data I want to store it in a table. I have some concerns:


What if i load 1 Jan - 31 Jan today, and then next week they change some data in that range? With thousands of products sold daily combing over that to look for necessary updates could be intense.
How should I manage adding new data? I'm thinking to get new data mid-month for the previous month. This vendor's practices are not the best, I'm concerned they'll add some things one Monday that they forgot to enter the previous Friday. I think if I get today's data every day the likelihood of changed data in a past period rises. 


Appreciate any advice from folks who've faced a similar issue. Maybe people do this all the time and I'm worried over nothing. Just would like to get some advice before I proceed.
Advice:


Normalize data stored.  
Consider carefully and figure out your write model.  For orders, can you overwrite?  do you need to mark superceded and append? 


The above are generic data entry pieces of advice, but regarding automated application to application interfaces, you have the issue of erroneous data entry.  To deal with this it is probably better to accept orders etc. but have the invoicing done by humans, who can cross check with the real world.  Also this keeps people in control of your books.  So I would add to that:


Separate automated entry from homan review and approval.