Question

我有一个Customers表，其中包含名为CustomerID，CustomerNumber的列。我有一个Orders表，它引用了Customers中的CustomerID表。

我需要查找并删除订单表中没有订单的CustomerNumber的所有重复记录。

这就是我在客户中找到我的副本的方式，但我不知道如何通过订单表过滤掉然后删除额外的记录：

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子句以检查没有关系的任何记录：

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

修改

如何删除以下记录的示例。对于符合上述条件的每条记录，这会将IsDeleted设置为1，并且不是customerid每CustomerNumber个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。为了获得更清晰的答案，您需要提供表格布局和关系。

{{1}}

Answer 2

这样的事情也可能有用：

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

注意：没有测试代码，可能需要调整。

查找/删除与另一个表没有关系的重复记录

2 个答案: