許多行到一行結果

Question

我希望我解釋得很好。我與此查詢掙扎：

我有這個表是這樣的：

InvoiceNum 
Amount 
Type - where type could be item, shipping or tax. 

所以要回到我是每張發票一行：InvoiceNum，ItemAmount，ShippingAmount，TAXAMOUNT。

下面是一個例子：

Invoicenum Amount Type 
1   $32 Item 
1   $2  Shipping 
1   $1  Tax 

我想返回：

InvoiceNum ItemAmount ShippingAmount TaxAmount 
1   $32  $2    $1 

Answer 1

可以總結與group by行，你可以使用case選擇特定的行：

select InvoiceNum 
,  sum(case when Type = 'Item' then Amount end) as ItemAmount 
,  sum(case when Type = 'Shipping' then Amount end) as ShippingAmount 
,  sum(case when Type = 'Tax' then Amount end) as TaxAmount 
from YourTable 
group by 
     InvoiceNum 

案例陳述返回null默認情況下，sum忽略空值。

Answer 2

你可以像@Andomar所顯示的那樣用group by和sum tricks（max works）來做到這一點。

或者，Microsoft SQL Server支持PIVOT操作的語法，該操作在此類查詢中有所幫助。儘管如此，您仍然需要對列名進行硬編碼。

SELECT InvoiceNum, [Item] AS ItemAmount, [Shipping] AS ShippingAmount, [Tax] AS TaxAmount 
FROM 
(SELECT InvoiceNum, Amount, Type FROM InvoiceTable) i 
PIVOT 
(
    MAX(Amount) 
    FOR Type IN ([Item], [Shipping], [Tax]) 
) AS pvt;