透視表返回所有空數據

Question

考慮這個查詢：

SELECT * 
FROM (
    SELECT 
    userid, 
    FORMAT(datecreated, 'yyyy-MM') AS purchasemonth, 
    COALESCE(amount + tip, 0) AS amt 
    FROM invoice 
) AS SourceTable 

產生的輸出是這樣的：

並在其中我想每個月總結在這個支點查詢：

SELECT 
    userid, 
    COALESCE([2016-08-01], 0) AS [2016-08-01], 
    COALESCE([2016-09-01], 0) AS [2016-09-01] 
FROM (
    SELECT 
    userid, 
    FORMAT(datecreated, 'yyyy-MM') AS purchasemonth, 
    COALESCE(amount + tip, 0) AS amt 
    FROM invoice 
) AS SourceTable 
PIVOT 
(
    SUM(amt) 
    FOR purchasemonth IN ([2016-08-01], [2016-09-01]) 
) AS PivotTable 

它產生如下輸出：

在原始查詢的輸出中根本沒有NULL數據。 PIVOT查詢的輸出只是空數據（合併爲0）。但我無法弄清楚爲什麼PIVOT沒有按照我的預期總結數據。我期待在PIVOT輸出中沒有NULL數據。

如何解決查詢的行爲與預期相符？

Answer 1

在派生表PurchaseMonth是字符串沒有它天你與天就相對於一個日期的值/列名：

所以主問題是這一行：

FOR purchasemonth IN ([2016-08-01], [2016-09-01]) 

TO

FOR purchasemonth IN ([2016-08], [2016-09]) 

一旦你改變，你會需要改變COALESCE()語句太

，你應該得到你想要的。

SELECT 
    userid, 
    COALESCE([2016-08], 0) AS [2016-08-01], 
    COALESCE([2016-09], 0) AS [2016-09-01] 
FROM (
    SELECT 
    userid, 
    FORMAT(datecreated, 'yyyy-MM') AS purchasemonth, 
    COALESCE(amount + tip, 0) AS amt 
    FROM invoice 
) AS SourceTable 
PIVOT 
(
    SUM(amt) 
    FOR purchasemonth IN ([2016-08], [2016-09]) 
) AS PivotTable 

如果你想01保持了天，然後簡單地改變了Derived Table定義爲一個日期或包括在格式

所以，如果你想要走這條路改變這一行的日子：

FORMAT(datecreated, 'yyyy-MM') AS purchasemonth,

要

DATEADD(day,1-DAY(datecreated),datecreated) AS purchasemonth,

你也可以使用這個

FORMAT(datecreated, 'yyyy-MM-dd') AS purchasemonth,

但FORMAT有，你沒有理由介紹，如果你並不需要性能的影響。

SELECT 
    userid, 
    COALESCE([2016-08-01], 0) AS [2016-08-01], 
    COALESCE([2016-09-01], 0) AS [2016-09-01] 
FROM (
    SELECT 
    userid, 
    DATEADD(day,1-DAY(datecreated),datecreated) AS purchasemonth, 
    COALESCE(amount + tip, 0) AS amt 
    FROM invoice 
) AS SourceTable 
PIVOT 
(
    SUM(amt) 
    FOR purchasemonth IN ([2016-08-01], [2016-09-01]) 
) AS PivotTable