SQL查询以获取特定列的默认值为0

Question

我正面临查询问题。

我的查询是： -

SELECT MONTH(o.OrderDate) as MonthValue, 
     YEAR(o.OrderDate) as YearValue, 
     C.CustomerTypeID, Count(o.Total) as NoOfOrders 
FROM Orders o   
RIGHT JOIN Customers C on C.CustomerID = o.CustomerID  

WHERE o.OrderDate >= CONVERT(DATETIME, '1/1/2013 00:00:00 AM') 
AND o.OrderDate <= CONVERT(DATETIME, '12/31/2013 23:59:59 PM') 
GROUP BY MONTH(o.OrderDate), 
     YEAR(o.OrderDate), 
     C.CustomerTypeID 
ORDER BY MONTH(o.OrderDate), 
     YEAR(o.OrderDate), 
     C.CustomerTypeID 

这是给结果如下： -

MonthValue YearValue CustomerTypeID NoOfOrders 
1    2013   1    10 
1    2013   2    20 
1    2013   3    45 
2    2013   1    45 
2    2013   2    45 
3    2013   1    88 
3    2013   2    56 
3    2013   3    89 

至于第2个月，客户类型3有没有结果，所以没有出现在结果。

但我想显示“0”作为其默认的结果，如下图所示： -

2    2013   3    0 

在此先感谢。

Answer 1

试试这个：

SELECT 2013 as [Year], 
     months.number, 
     Amount = SUM(COALESCE(o.Total,0)), 
     C.CustomerType 
FROM Customers C 
CROSS JOIN 
(SELECT number FROM master..spt_values WHERE type='p' and number between 1 and 12) months 
LEFT JOIN [Orders] o on C.CustomerId = o.CustomerId and YEAR(o.OrderDate) = 2013 and MONTH(o.OrderDate) = months.number 
GROUP BY months.number, C.CustomerType 
ORDER BY months.number, C.CustomerType 

Answer 2

那么你可以做一个完整的外部联接，它应该会给你所有的客户，为缺失的数据重新调用null。然后你可以选择ISNULL（NoOfOrders，0）来得到0而不是null。

我不是100 &当然可以，但你可以试一试。

Answer 3

编辑：你必须外部连接所有月份获取缺少的条目。因此为了获得最佳可读性，请先交叉所有客户和月份，然后再外部加入订单。

SELECT all_months.MonthValue, 
     all_months.YearValue, 
     C.CustomerTypeID, 
     Count(o.Total) as NoOfOrders 
FROM 
(
    SELECT distinct MONTH(OrderDate) as MonthValue, YEAR(OrderDate) as YearValue 
    FROM orders 
    WHERE YEAR(OrderDate) = 2013 
) all_months   
CROSS JOIN Customers C 
LEFT OUTER JOIN Orders o 
    ON o.CustomerID = C.CustomerID 
    AND MONTH(o.OrderDate) = all_months.MonthValue 
    AND YEAR(o.OrderDate) = all_months.YearValue 
GROUP BY all_months.MonthValue, 
     all_months.YearValue, 
     C.CustomerTypeID 
ORDER BY all_months.MonthValue, 
     all_months.YearValue, 
     C.CustomerTypeID ;