How to calculate average date occurrence frequency in SQL.
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I'm trying to produce a query on the following table (relevant portion only):

    Create Table [Order] (
      OrderID int NOT NULL IDENTITY(1,1),
      CreationDate datetime NOT NULL,
      CustomerID int NOT NULL
    )

I would like to see a list of CustomerIDs with each customer's average number of days between orders. I'm curious if this can be done with a pure set based solution or if a cursor/temp table solution is necessary.  



