多個SQL SELECT WHERE與相交，佔位符值

Question

我使用SQL服務器，我試圖做到以下幾點：

SELECT dword FROM Details WHERE dskey = '51a' 
INTERSECT 
SELECT dword FROM Details WHERE dskey = '52b' 
INTERSECT 
SELECT dword FROM Details WHERE dskey = '53i' 
INTERSECT 
SELECT dword FROM Details WHERE dskey = '54d' 
INTERSECT 
SELECT dword FROM Details WHERE dskey = '55e'; 

這工作得很好。不過，我需要建立一個通用的選擇，如：

SELECT dword FROM Details WHERE dskey = value1 
INTERSECT 
SELECT dword FROM Details WHERE dskey = value2 
INTERSECT 
SELECT dword FROM Details WHERE dskey = value3 
INTERSECT 
SELECT dword FROM Details WHERE dskey = value4 
INTERSECT 
SELECT dword FROM Details WHERE dskey = value5; 

然而，在任何給定的執行，我可能不會有所有的5個關鍵值。我需要擁有不會干擾INTERSECT的虛設鍵值。

例如，假設我只有1個值，其餘4個都是空的。但INTERSECT沒有（正確）工作。

是否有虛擬值不會干擾INTERSECTS。

我討厭必須做嵌套的ifs，如果我只有一個值，我只執行一個SELECT。如果我有兩個值，那麼我有兩個選擇與Intertering INTERSECT等。

以下是這是怎麼一回事：

說我有5個字符的話，我希望能夠做一個選擇在何處返回的說不說都5個字符的單詞列表的「I」第三個位置。很簡單。那麼我可能想要選擇第三個位置是'我'，第五個是'e'。這就像「幸運之輪」。我可能擁有所有五個值a-b-i-d-e，所以返回的集合只應該遵守。因此，最好有一組5個SELECTS和4個介入INTERSECTS，這個結構可以處理1到5個值。

我試過NULL值，顯然不工作，因爲它不應該。

Answer 1

戈登這個工作就像一個魅力！

use wofwords; 
go 

DECLARE @value1 varchar(25) = '51a'; 
DECLARE @value2 varchar(25) = '52b'; 
DECLARE @value3 varchar(25) = NULL; 
DECLARE @value4 varchar(25) = NULL; 
DECLARE @value5 varchar(25) = NULL; 


SELECT dword FROM Details WHERE dskey = @value1 or @value1 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value2 or @value2 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value3 or @value3 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value4 or @value4 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value5 or @value5 IS NULL; 
go 

它給我正確答案和最重要的是，我現在可以編寫了C＃的一部分，有一個單獨的查詢，而不是嵌套IFS ...

約翰尼

Answer 2

你也可以構造查詢爲：

SELECT dword 
FROM Details 
WHERE dskey IN (value1, value2, value3, value4, value5) 
GROUP BY dword 
HAVING COUNT(DISTINCT dskey) = 5; 

你仍然需要更換IN列表，你可以寫這個使用明確的參數個數5：

WITH vals as (
     SELECT v.val 
     FROM (VALUES (@value1), (@value2), (@value3), (@value4), (@value5)) v(val) 
    ) 
SELECT dword 
FROM Details d JOIN 
    vals 
    ON d.dskey = vals.val 
GROUP BY dword 
HAVING COUNT(DISTINCT dskey) = (SELECT COUNT(*) FROM vals); 

這是完全可參數化並處理NULL值。

編輯：

其實，你可以用你的版本也這麼做：

SELECT dword FROM Details WHERE dskey = @value1 or @value1 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value2 or @value2 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value3 or @value3 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value4 or @value4 IS NULL 
INTERSECT 
SELECT dword FROM Details WHERE dskey = @value5 or @value5 IS NULL; 

相交的所有行是路口無操作。