T-sql case返回錯誤值

Question

我努力讓我的SQL查詢工作。當我的IN FAILS找到一行時，我想返回一行，就像圖片中的行一樣，但是我想將ifuserholdscertificate設置爲「NO」。

SELECT tuc.id, 
     tu.firstName, 
     tuc.uid, 
     tuc.value, 
     tc.name, 
     count(tuc.value) over (PARTITION BY tuc.uid) AS 'amount', 
     'certificate DESIRABLE' AS 'typeofthing' , 
     'YES' AS 'HasorNot', 
     ifuserholdscertificate = CASE 
            WHEN count(tuc.value) = 0 THEN 'NO' 
            ELSE 'YES' 
           END 
FROM t_user_certificates tuc, 
    t_certificates tc, 
    t_users tu 
WHERE tuc.value IN (4, 
        12, 
        31) 
    AND tuc.value = tc.id 
    AND tu.id = tuc.uid 
GROUP BY tuc.id, 
     tu.firstName, 
     tuc.uid, 
     tuc.value, 
     tc.name 

這是查詢生成的數據！

正如你可以看到，即使有些人只有在金額行中得到2，它仍然不會獲取一行並將ifuserholdscertificate設置爲'NO'。

根據要求更新！

select tuc.id, 
count(tuc.value) as 'counten', 
tu.firstName, 
tuc.uid, 
tuc.value, 
tc.name, 
count(tuc.value) over (PARTITION BY tuc.uid) as 'amount', 
'certificateDESIRABLE' as 'typeofthing' , 
'YES' as 'HasorNot', 
HasOrders = CASE 
       WHEN count(tuc.value) = 0 THEN 'NO' 
       ELSE 'YES' 
      END 
from t_user_certificates tuc     
left outer join t_certificates tc 
on tuc.value = tc.id 
left outer join t_users tu 
on tu.id = tuc.uid 
GROUP BY tuc.id, tu.firstName, tuc.uid, tuc.value, tc.name 

Alwyas一個1伯爵始終 'YES'

Answer 1

這可能是更喜歡你在找什麼。你總是返回1，並且沒有用戶沒有證書，因爲你在where子句中有IN位。因此，即使使用外部聯接，也只能使用這些值從t_user_certificates返回行。它有效地成爲一個內部連接。 ANSI連接語法是你的朋友。它將JOIN邏輯從過濾器中分離出來。

SELECT tuc.id, 
     tu.firstName, 
     tuc.uid, 
     tuc.value, 
     tc.name, 
     count(tuc.value) AS 'amount', 
     'certificate DESIRABLE' AS 'typeofthing' , 
     'YES' AS 'HasorNot', 
     ifuserholdscertificate = CASE 
            WHEN count(tuc.value) > 0 THEN 'YES' 
            ELSE 'NO' 
           END 
FROM 
    t_users tu 
LEFT JOIN t_user_certificates tuc 
    ON 
    tu.id = tuc.uid 
    AND 
    tuc.value IN 
    (
     4 
     , 12 
     , 31 
    ) 
LEFT JOIN 
    t_certificates tc 
    ON 
    tuc.value = tc.id 

GROUP BY tuc.id, 
     tu.firstName, 
     tuc.uid, 
     tuc.value, 
     tc.name; 

Answer 2

你可能會得到空值，而不是零，你不佔。我反而試試這個：

ifuserholdscertificate = CASE         
    WHEN (count(tuc.value) = 0 or count(tuc.Value) = null) THEN 'NO' 
    ELSE 'YES' 
    END 

我沒有得到爲什麼就表示人得到2雖然然後佔零和期待一個「NO」的回答。如果不瞭解所收集的源數據，很難在引用它之前知道數據的外觀。你也使用了一個窗口函數（over（partion by ..）），它會給出與常規計數函數不同的數據。如果您的目標是在窗口函數上使用表達式時需要使用一種情況，那麼您必須先執行嵌套select或cte來先獲取數字，然後再對其進行邏輯處理。

事情是這樣的：

declare @Person Table (personID int identity, person varchar(8)); 

insert into @Person values ('Brett'),('Sean'),('Chad'); 

declare @Orders table (OrderID int identity, PersonID int, Desciption varchar(32), Amount int); 

insert into @Orders values (1, 'Shirt', 20),(2, 'Shirt', 22),(2, 'Shoes', 52); 

With a as 
    (
    Select 
     p.person 
    , count(o.orderID) over(partition by person) as Count 
    from @Person p 
     left join @Orders o on p.personID = o.PersonID 
    ) 
select 
    person 
, case when Count = 0 then 'No' else cast(Count as varchar(8)) end as Count 
from a 

Answer 3

到您的查詢添加列調試。並用你的屏幕截圖顯示這些結果。

MyCOUNT = count(tuc.value), 

我的Northwind示例工作正常。當父母客戶沒有訂單（行）時，我得到「否」。

................

Use Northwind 
GO 

Select 
    custs.CustomerID, 
    MyCOUNT = count(ords.OrderID), 
    HasOrders = CASE 
     WHEN count(ords.OrderID) = 0 THEN 'NO' 
     ELSE 'YES' 
    END 
from 
    [dbo].[Customers] custs left outer join [dbo].[Orders] ords on custs.CustomerID = ords.CustomerID 
GROUP BY 
    custs.CustomerID 
order by 2 

這裏有一些額外的查詢顯示上的是什麼打算：

Select Label = 'You get no results here', custs.CustomerID , ords.OrderID 
from 
    [dbo].[Customers] custs join [dbo].[Orders] ords on custs.CustomerID = ords.CustomerID 
Where 
    ords.OrderID IS NULL 


Select Label = 'You get Customers with no Orders here', custs.CustomerID , ords.OrderID 
from 
    [dbo].[Customers] custs left outer join [dbo].[Orders] ords on custs.CustomerID = ords.CustomerID 
Where 
    ords.OrderID IS NULL 


Select Label = 'You get Customers with or without Orders here', custs.CustomerID , ords.OrderID 
from 
    [dbo].[Customers] custs left outer join [dbo].[Orders] ords on custs.CustomerID = ords.CustomerID 

在這裏你可以得到酒吧和Northwind數據庫。 這很有幫助，因爲大多數開發人員已經安裝了這些數據庫（和AdventureWorks）來處理這種情況。

http://msdn.microsoft.com/en-us/library/ms143221(v=sql.105).aspx