查詢結果是單行還是多個值，逗號分隔

Question

我有三個具有以下結構的表（商店，銷售和產品）：

--Stores
IdStore   StoreName
1A        Store A
2B        Store B
3C        Store C

-- Products
IdProduct   Desc
1G          Product 1
2A          Product 2
3A          Product 3
4A          Product 4

--Sales
TicketNo  Store     Product     Qty
1001      Store A   Product 1   10
1002      Store A   Product 1   10
1003      Store B   Product 3   50
1004      Store A   Product 2   20
1005      Store A   Product 3   5
1006      Store B   Product 1   30

目前，我有以下查詢：

SELECT S.StoreName, sum(SA.Qty), P.Desc
FROM SALES SA
cross apply (select top 1 * from Stores S where SA.Store = S.StoreName) S
cross apply (select top 1 * from Products P where SA.Product = P.Desc) P
group by S.StoreName, P.Desc

根據上面的表結構和數據，查詢結果如下：

-- output
StoreName    Qty   Desc
Store A      20    Product 1
Store A      20    Product 2
Store A      5     Product 3
Store B      30    Product 1
Store B      20    Product 2

我的問題是，是否存在一種獲得相同結果但順序不同的方法，以及是否有可能從一行中的一個商店中獲取所有結果，如下所示：

Store    Product 1  Product 2  Product 3
Store A  20         20         5    
Store B  30         20         0

或類似的東西：

Store     Result (in same line)
Store A   20;20;5;
Store B   30;20;0;

Answer 1

首先，您應該使用INNER JOIN而不是CROSS APPLY：

SELECT S.StoreName, P.Desc,sum(SA.Qty) as QTY
FROM SALES SA
    INNER JOIN Stores S ON SA.Store = S.StoreName
    INNER JOIN Products P ON SA.Product = P.Desc
group by S.StoreName, P.Desc

如果預先知道列數，則可以使用PIVOT運算符將行轉換為列：

SELECT S.StoreName, [Product 1], [Product 2], [Product 3]
FROM 
( SELECT SA.StoreName, P.Desc,SA.Qty
  FROM SALES SA
    INNER JOIN Stores S ON SA.Store = S.StoreName
    INNER JOIN Products P ON SA.Product = P.Desc
) Q
PIVOT 
(
    SUM(Qty)
    FOR Q.Desc IN ([Product 1], [Product 2], [Product 3])
) AS pvt
ORDER BY StoreName

坦率地說，在客戶端上生成適當的表可能會更容易。 PIVOT無法處理任意數量的列。 另一方面，在ASP.NET中，可以使用LINQ等按商店和產品對數據進行分組，然后根據該數據生成表行。 如果使用了像Entity Framework這樣的ORM，則數據將已經處於適當的結構中。

生成所需表可以使用兩個循環，例如：

<thead>
    <tr>
        <th>Store Name</th>
        <th>Product 1</th>
        ...
    </tr>
</thead>
@foreach(var store in Model.Stores)
{
    <tr>
        <td>@store.StoreName</td>
        @foreach(var product in store.Products.OrderBy(p=>p.Desc))
        {
           <td>@product.Qty</td>
        }
    </tr>
}

您可以使用LINQ獲得所有產品名稱，例如：

var productNames = Stores.SelectMany(store=>store.Products)
                         .Select(p=>p.Desc)
                         .Distinct()
                         .OrderBy(desc=>desc)
                         .ToArray();

並使用它們在循環中自己生成標頭

Answer 2

干得好。 您將需要PIVOT功能，但是您需要定義產品的名稱。

請參見下面的樣機：

DECLARE @Stores TABLE(IdStore VARCHAR(100),[StoreName] VARCHAR(100));
INSERT INTO @Stores 
--Stores
select '1A','Store A' UNION ALL
select '2B','Store B' UNION ALL
select '3C','Store C'


DECLARE @Products TABLE(IdProduct VARCHAR(100),[Desc] VARCHAR(100));
INSERT INTO @Products 
-- Products
select '1G','Product 1' UNION ALL
select '2A','Product 2' UNION ALL
select '3A','Product 3' UNION ALL
select '4A',' Product 4'

DECLARE @Sales TABLE(TicketNo INT, Store  VARCHAR(100),[Product] VARCHAR(100), Qty INT);
INSERT INTO @Sales
--Sales
select '1001','Store A','Product 1','10' UNION ALL
select '1002','Store A','Product 1','10' UNION ALL
select '1003','Store B','Product 3','50' UNION ALL
select '1004','Store A','Product 2','20' UNION ALL
select '1005','Store A','Product 3','5' UNION ALL
select '1006','Store B','Product 1','30'




SELECT p.*
FROM 
(
    SELECT S.StoreName, SA.Qty, P.[Desc]
    FROM
        @SALES SA
    left join @Stores S on SA.Store = S.StoreName
    left join  @Products P on SA.Product = P.[Desc] 

)t
PIVOT
(
    SUM(Qty) FOR [Desc] IN ([Product 1],[Product 2],[Product 3] /*add as many as you need*/)
)p;