# Need for Data Warehouse Amazon CEO wants to know the sales of the new Kindle Scribe reader they launched this year compared to other eReaders in the next 30 mins. Where do we look for this info? * Transactional databases use every resource to serve customers. Querying on them may slow down a customer's request. * Also, they are Live databases. So they may or may not have historical data. * Chances are data format may differ for each region/country in which Amazon is doing business in. It's not just Amazon; it's everywhere. * Airlines * Bank Transactions / ATM transactions * Restaurant chains, and so on. Companies will have multiple databases that are not linked with each other for specific reasons. * Sales Database * Customer Service Database * Marketing Database * Inventory Database * Human Resources Database There is no reason for linking HR data to Sales data, but the CFO might need this info for budgeting. *Fun Qn: How many times have you received Marketing mail/email from the same company you have an account with?* --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://gchandra.gitbook.io/data-warehousing/fundamentals/what-is-a-data-warehouse/need-for-data-warehouse.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.