Depending on the time frame requested, you would convert an order date into specific interval (week #+year, month+year, quarter+year, or year) and group on it

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>I have a standard SQL table holding customer orders. The table has a customerID, an order date, and an order quantity. I would like to create a query that would give me a count of orders and a total amount of orders for 'n' number of days within a date range. For example, I want to see a weekly count (# of days would be 7) for orders for each customer starting Jan 1, 2011 up to today.
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>I could say that maybe my variable time frames would be weekly, monthly, quarterly or yearly.
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