使用此查询,我的输出包括 COUNT 为 0 的所有值,但我仍然收到未包含 Null 值的警告。双连接是为了让表适当链接以计算订单数,但我也想包括所有 NULL,而不仅仅是 COUNT 为 0 的地方。我错过了什么?
SELECT EmpNo, LastName, COUNT(CustomerOrder.OrderNo)
FROM Employee
LEFT OUTER JOIN Customer
ON Customer.AcctRepNo = EmpNo
LEFT OUTER JOIN CustomerOrder
ON Customer.CustNo =CustomerOrder.CustNo
GROUP BY EmpNo, LastName
ORDER BY COUNT(CustomerOrder.OrderNo) DESC, LastName