sql - 如何获取缺失的汇总数据

Question

我有一个查询，按月提供总销售额。但是，有些月份没有销售。我如何在查询结果中获得该月的 0 值？

SELECT
    p.Part,
    SUM(s.Sales) AS Sales,
    MONTH(s.SalesDate) AS Month_Sold
FROM
    Parts p
    LEFT OUTER JOIN Sales s ON p.Part = s.Part
GROUP BY
    p.Part,
    MONTH(s.SalesDate)
ORDER BY
    p.Part,
    Month_Sold

Answer 1

这样做是SUM(ISNULL(s.Sales, 0))为了使您的 NULL 值不会被聚合消除。虽然，由于您也依赖于您的销售数据中的月份，您将需要查找月份，以便您可以查看所有月份，即使您的销售数据中没有它们。

所以，像这样：

    ;WITH months AS
    (
        SELECT 1 AS mo
        UNION ALL
        SELECT mo +1
        FROM months
        WHERE mo < 12
    )

    SELECT p.Part, SUM(s.Sales) AS Sales, mo AS Month_Sold 
    FROM Parts p 
    CROSS APPLY months
    LEFT OUTER JOIN Sales s 
        ON p.Part = s.Part 
        AND months.mo = MONTH(s.SalesDate) 
    GROUP BY p.Part, months.mo ORDER BY p.Part, Month_Sold