Fill In The Date Gaps With Date Table

Question

I have two tables.

An orders table with customer, and date. A date dimension table from a data warehouse.

The orders table does not contain activity for ev

Answer 1

The problem is that you need all customers for all dates. When you do the left outer join, you are getting NULL for the customer field.

The following sets up a driver table by cross joining the customer names and dates:

SELECT driver.customer, driver.fulldate, o.amount 
FROM   (select d.fulldate, customer
        from datetable d cross join
             (select customer
              from orders
              where year(orderdate) in (2012)
             ) o
        where d.calendaryear IN ( 2012 )
       ) driver LEFT OUTER JOIN
       orders o 
       ON driver.fulldate = o.orderdate and
          driver.customer = o.customer;

Note that this version assumes that calendaryear is the same as year(orderdate).