查找/刪除與另一個表無關的重複記錄

Question

我有一個Customers表，其中有一個名爲CustomerID，CustomerNumber的列。我有一個Orders表，它引用了Customers中的CustomerID表。

我需要找到並刪除訂單表中沒有訂單的CustomerNumber的所有重複記錄。

這是我如何找到我的副本在客戶，但我不知道如何通過訂單表過濾掉，然後刪除多餘的記錄：

SELECT Name, CustomerNumber, COUNT(*) As DupeCount 
FROM StagingCustomers 
WHERE ManufacturerID=15 
GROUP BY Name, CustomerNumber 
HAVING COUNT(CustomerNumber) > 1 
ORDER BY CustomerNumber 

Answer 1

添加EXISTS子句來檢查任何記錄沒有關係：

SELECT Name, CustomerNumber, COUNT(*) As DupeCount 
FROM StagingCustomers S 
WHERE ManufacturerID=15 
AND NOT EXISTS (SELECT 1 from Orders WHERE CustomerID = S.CustomerID) 
GROUP BY Name, CustomerNumber 
HAVING COUNT(CustomerNumber) > 1 
ORDER BY CustomerNumber 

編輯：

如何刪除記錄是例低。對於符合上述標準的每條記錄，這將設置IsDeleted爲1，AND不是最低的customerid每CustomerNumber。爲了更清晰的回答，你需要給你的表格佈局和關係。

UPDATE S 
SET IsDeleted = 1 
FROM StagingCustomers S 
WHERE ManufacturerID=15 
AND NOT EXISTS (SELECT 1 from Orders WHERE CustomerID = S.CustomerID) 
AND CustomerID NOT IN (SELECT CustomerNumber, MIN(CustomerID) 
         FROM StagingCustomers 
         GROUP BY CustomerNumber) 
GROUP BY Name, CustomerNumber 
HAVING COUNT(CustomerNumber) > 1 
ORDER BY CustomerNumber 

Answer 2

像這樣的東西可能工作太：

SELECT Name, CustomerNumber, COUNT(*) As DupeCount 
FROM StagingCustomers AS SC 
LEFT JOIN ORDERS AS OD ON SC.CustomerID = OD.CustomerID 
WHERE OD.CustomerID IS NULL AND ManufacturerID = 15 
GROUP BY Name, CustomerNumber 
HAVING COUNT(CustomerNumber) > 1 
ORDER BY CustomerNumber 

注：沒有測試的代碼，可能需要調整。