SELECT語句檢索什麼從來沒有發生過

Question

我CallHistory表，這些列：

CustomerId, TimeOfCall, CallResult 

和CallResult我可能有這樣的值： 「下的訂單」，「要求退貨」，「技術問題」， '詢問價格'等。

我想SELECT CustomerId FROM CallHistory WHERE客戶至少有一次「詢問價格」，但從來沒有「放置訂單」。

謝謝！

Answer 1

我想你應該能夠用單一選擇不連接或子

做試試這個：

SELECT CustomerId 
FROM CallHistory 
GROUP BY CustomerId 
HAVING COUNT(CASE WHEN CallResult='Inquired about Pricing' THEN 1 ELSE NULL END) > 0 
    AND COUNT(CASE WHEN CallResult='Placed Order' THEN 1 ELSE NULL END) = 0 

Answer 2

SELECT DISTINCT c.CustomerId 
    FROM CallHistory c 
    WHERE c.CallResult = 'inquired about Pricing' 
     AND NOT EXISTS(SELECT 1 
          FROM CallHistory c2 
          WHERE c2.CustomerId = c.CustomerId 
           AND c2.CallResult = 'Placed Order') 

Answer 3

SELECT CustomerId 
    FROM CallHistory 
WHERE CallResult = 'Inquired about Pricing' 
EXCEPT 
SELECT CustomerId 
    FROM CallHistory 
WHERE CallResult = 'Placed Order';