如何在Access查詢結果中包含空行

Question

我有一個包含客戶端信息的Access 2010數據庫。我需要創建一個每個時代的客戶數量表。我要報告的機構需要報告每個年齡從0到100歲的客戶數量。下面的SQL查詢將創建所需的報表，但不包括具有零客戶端的年齡。

SELECT AgeNum & " years" AS [Age], Count(*) AS [Count] 
FROM (SELECT Int(DateDiff("d", Clients.dob, now())/365.25) AS AgeNum 
FROM Clients) AS [%$##@_Alias] 
GROUP BY [%$##@_Alias].AgeNum; 

如何讓查詢返回Count列中0的空行？

我環顧四周，發現這一點：

How can I create a row for values that don't exist and fill the count with 0 values?

他們創造價值的一個表中查找空組。這是非常相似，我需要的只是它什麼使用不是在Access支持的凝聚功能，2010年

Answer 1

系統知道存在某個特定記錄的年齡。如果你想有一個年齡在1到100之間的列表，你需要告訴或提供你正在尋找0..100年齡的系統。通過提供您正在查找的年齡列表，如果在查找到的記錄中未找到請求的年齡，系統將自動返回0/null。

正如其他人提到的，你可以有一個1..100行的表格，並在你的SQL中進行比較，或者你可以用SQL生成一個數字列表。

某些DBMS提供了一個名爲dual的默認表，它具有一列和一行，您可以將該表用於任何沒有表的表。 在您的訪問應用程序中，創建一個名爲「dual」的表並插入一行。

現在執行這個查詢：

SELECT TMain.counter 
FROM (SELECT (T2.mAge*t3.mFactor10)+t1.mAge AS counter 
FROM (select 1 as mAge from dual 
union all select 2 from dual 
union all select 3 from dual 
union all select 4 from dual 
union all select 5 from dual 
union all select 6 from dual 
union all select 7 from dual 
union all select 8 from dual 
union all select 9 from dual 
union all select 10 from dual) AS T1, 
(select 0 as mAge from dual 
union all select 1 from dual 
union all select 2 from dual 
union all select 3 from dual 
union all select 4 from dual 
union all select 5 from dual 
union all select 6 from dual 
union all select 7 from dual 
union all select 8 from dual 
union all select 9 from dual 
union all select 10 from dual) AS T2, 
(select 10 as mFactor10 from dual) AS T3) AS TMain 
WHERE (((TMain.counter) Between 1 And 100)); 

這將從1..100產生100行。

然後，您可以將此結果用作SQL的外部表，並查找/計算年齡在此列表中的任何人。 邏輯是：

select all age 
from the reqeusted age list 
find and count/return all matched records or return 0 if no records found. 

在SQL中，這將是這樣的，

SELECT TMain.counter as Age, 
(SELECT Count(*) AS [Count] 
FROM (SELECT Int(DateDiff("d", Clients.dob, now())/365.25) AS AgeNum 
FROM Clients) AS [%$##@_Alias] 
WHERE (TMain.counter = [%$##@_Alias].ageNum) 
GROUP BY [%$##@_Alias].AgeNum) as number_of_clients 
FROM (SELECT (T2.mAge*t3.mFactor10)+t1.mAge AS counter 
FROM (select 1 as mAge from dual 
union all select 2 from dual 
union all select 3 from dual 
union all select 4 from dual 
union all select 5 from dual 
union all select 6 from dual 
union all select 7 from dual 
union all select 8 from dual 
union all select 9 from dual 
union all select 10 from dual) AS T1, 
(select 0 as mAge from dual 
union all select 1 from dual 
union all select 2 from dual 
union all select 3 from dual 
union all select 4 from dual 
union all select 5 from dual 
union all select 6 from dual 
union all select 7 from dual 
union all select 8 from dual 
union all select 9 from dual 
union all select 10 from dual) AS T2, 
(select 10 as mFactor10 from dual) AS T3) AS TMain 
WHERE (((TMain.counter) Between 1 And 100)); 

這將產生：從1..100年齡以及客戶端的數量各年齡和null爲空/空無結果。 當然，您可以動態擴展或縮短年齡列表。

Answer 2

你可以用它代替COALESCENz功能：

Nz([Age],0) 

是的，你的鏈接應該工作您。

Answer 3

創建一個包含所有可能整數的「序列」表（在英國醫學數據字典中使用FYI，我們使用220作爲年限的最大年齡），然後對此表進行「反加入」。您可以使用視圖來獲取原始結果。

下面的SQL DDL需要ANSI-92查詢模式（可能比默認查詢模式在SQL Server編碼器更好），但也可以使用Access GUI工具maually創建：僅

CREATE TABLE Seq (seq INT NOT NULL UNIQUE); 


INSERT INTO Seq VALUES (1); 
INSERT INTO Seq VALUES (2); 
INSERT INTO Seq VALUES (3); 
... 
(you can use Excel to create this script!) 
... 
INSERT INTO Seq VALUES (100); 


CREATE VIEW ClientAgeTallies (AgeInYears, Tally) 
AS 
SELECT dt.AgeInYears, COUNT(*) AS Tally 
    FROM (SELECT INT(DATEDIFF('d', c.dob, NOW())/365.25) AS AgeInYears 
      FROM Clients AS c) AS dt 
GROUP 
    BY dt.AgeInYears; 


SELECT AgeInYears, Tally 
    FROM ClientAgeTallies 
UNION 
SELECT seq AS AgeInYears, 0 AS Tally 
    FROM Seq 
WHERE seq NOT IN (SELECT AgeInYears FROM ClientAgeTallies);