T-SQL，零和，联接时不匹配

Question

我有两张桌子，一张有我所有的分店，一张有我所有的销售额。 该销售表还包含一个销售代表ID，一个分支ID，一个月和一年。

我需要一个查询，该查询将返回特定代表的一年的销售总额（按分支机构和月份分组），并且如果该月的分支机构中没有销售，则查询必须返回0。 我有以下内容，如果没有销售，则不会返回0：

SELECT
    s.Month,
    b.BranchName,
    SUM(s.InvoiceAmount) AS 'Sales'
FROM 
    Branch b
INNER JOIN
    Sales s ON s.BranchID = b.BranchID
WHERE
    s.Year = 2008
AND
    s.SalesRepID= 11
GROUP BY 
    s.Month,
    b.BranchName
ORDER BY 
    s.Month,
    b.BranchName

Answer 1

您将需要添加“缺失”数据才能加入它。

SELECT
    b.BranchName,
    SUM(ISNULL(s.InvoiceAmount, 0)) AS 'Sales',
    s.Month
FROM 
    Branch b
    LEFT OUTER JOIN (
            SELECT
        b.BranchID AS BranchID
        , s.SalesRepID AS SalesRepID
        , Months.Month AS Month
        , Years.Year AS Year
        , 0 AS InvoiceAmount
      FROM 
          Sales s
          CROSS JOIN (
            SELECT 1 AS Month
            UNION ALL SELECT 2
            UNION ALL SELECT 3
            UNION ALL SELECT 4
            UNION ALL SELECT 5
            UNION ALL SELECT 6
            UNION ALL SELECT 7
            UNION ALL SELECT 8
            UNION ALL SELECT 9
            UNION ALL SELECT 10
            UNION ALL SELECT 11
            UNION ALL SELECT 12
            ) Months
          CROSS JOIN (
            SELECT 2007 AS Year
            UNION ALL SELECT 2008
            UNION ALL SELECT 2009
            ) Years
          CROSS JOIN Branch b
      UNION ALL SELECT 
        s.BranchID AS BranchID
        , s.SalesRepID AS SalesRepID
        , s.Month AS Month
        , s.Year AS Year
        , s.InvoiceAmount AS InvoiceAmount
      FROM Sales s      
    )s ON s.BranchID = b.BranchID    
WHERE
    s.Year = 2008
    AND s.SalesRepID= 11
GROUP BY 
    s.Month,
    b.BranchName
ORDER BY 
    b.BranchName,
    s.Month

Answer 2

您需要对Sales进行LEFT JOIN，以便甚至返回在Sales表中没有任何记录的代表。

Answer 3

如果查询返回NULL，则可以使用一种合并方法： COALESCE(SUM(...), 0)将返回列表中的第一个非NULL值...

Answer 4

我将联接从内部更改为外部，并为没有销售的分支添加了ISNULL函数。

SELECT

    b.BranchName,
    s.Month,
    SUM(ISNULL(s.InvoiceAmount,0)) AS 'Sales'
FROM 
    Branch b
LEFT JOIN
    Sales s ON s.BranchID = b.BranchID
WHERE
    s.Year = 2008
AND
    s.SalesRepID= 11
GROUP BY 
    s.Month,
    b.BranchName
ORDER BY 
    s.Month,
    b.BranchName

Answer 5

您需要使用左连接和一个非null来使总和正确：

SELECT    b.BranchName
,    SUM(isnull(s.InvoiceAmount, 0)) AS 'Sales'
FROM     Branch b
LEFT JOIN    Sales s ON s.BranchID = b.BranchID 
GROUP BY     s.Month,    b.BranchName
ORDER BY     s.Month,    b.BranchName

如果推销员在特定月份内没有销售，您仍然需要做更多的工作来显示月份。