sql - 用日期表填补日期空白

Question

我有两张 table 。

带有客户和日期的订单表。
来自数据仓库的日期维度表。

订单表不包含给定月份中每个日期的事件，但我需要返回一个结果集来填补日期和客户的空白。

例如，我需要这个:

Customer   Date
===============================
Cust1       1/15/2012   
Cust1       1/18/2012
Cust2       1/5/2012
Cust2       1/8/2012

To look like this:

Customer   Date
============================
Cust1       1/15/2012   
Cust1       1/16/2012   
Cust1       1/17/2012       
Cust1       1/18/2012
Cust2       1/5/2012
Cust2       1/6/2012
Cust2       1/7/2012
Cust2       1/8/2012

This seems like a left outer join, but it is not returning the expected results. Here is what I am using, but this is not returning every date from the date table as expected.

SELECT o.customer, 
       d.fulldate
FROM   datetable d 
       LEFT OUTER JOIN orders o 
                    ON d.fulldate = o.orderdate 
WHERE  d.calendaryear IN ( 2012 ); 

Answer 1

问题是您需要所有日期的所有客户。当您执行 left outer join 时，客户字段为 NULL。

下面通过 cross join ing 客户姓名和日期设置驱动程序表:

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;

请注意，此版本假定 calendaryear 与 year(orderdate) 相同。