Question

退回至少有2个不同订单的员工，其中订单上的某些产品的数量> = 5。

 * Format:
 * EmployeeId, EmployeeName, orderCount

到目前为止我写过：

ResultSet rst = stmt.executeQuery("SELECT Employee.EmployeeId,EmployeeName, COUNT(DISTINCT Orders.EmployeeId) as orderCount "
                + "FROM Employee,Orders,OrderedProduct"
                + " WHERE quantity >=5 AND Employee.EmployeeId = Orders.EmployeeId AND Orders.OrderId = OrderedProduct.OrderId"
                + " GROUP BY OrderedProduct.OrderId,Employee.EmployeeId,EmployeeName");

我得到了结果：

EmployeeId, EmployeeName, orderCount

E0002, E. Edwards, 1

E0007, I. Irvin, 1

E0006, D. Davis, 1

E0001, B. Bogart, 1

E0006, D. Davis, 1

但我正在寻找的是

OrderId, EmployeeId, EmployeeName, orderCount

E0006, D. Davis, 2

我无法弄清楚如何计算D.戴维斯两次，真的很感激一些帮助

Answer 1

您应该过滤添加HAVING COUNT(DISTINCT Orders.EmployeeId) > 1

的结果

ResultSet rst = stmt.executeQuery("SELECT Employee.EmployeeId, EmployeeName, COUNT(DISTINCT Orders.OrderId) as orderCount "
              + " FROM Employee,Orders,OrderedProduct"
              + " WHERE quantity >=5 AND Employee.EmployeeId = Orders.EmployeeId AND Orders.OrderId = OrderedProduct.OrderId"
              + " GROUP BY Employee.EmployeeId,EmployeeName"
              + " HAVING COUNT(DISTINCT Orders.OrderId) >1 ");

Answer 2

首先，从不在FROM子句中使用逗号。始终使用正确的，明确的JOIN语法。对于此查询，您可以执行以下操作：

SELECT e.EmployeeId, e.EmployeeName, COUNT(DISTINCT o.OrderId) as orderCount
FROM Employee e JOIN
     Orders o
     ON e.EmployeeId = o.EmployeeId JOIN
     OrderedProduct op
     ON o.OrderId = op.OrderId
GROUP BY e.EmployeeId, e.EmployeeName
HAVING COUNT(DISTINCT o.OrderId) > 1 AND MAX(quantity) >= 5;

你应该明白这是如何运作的。要计算订单，您需要计算OrderId秒。 <{1}}上的条件必须在 quantity之后发生。

退回至少有2个不同订单的员工，其中订单上的某些产品的数量> = 5

2 个答案: