从 MySQL 获取查询到 Java

Question

I created a query on MySQL workbench, it worked fine, but when I tried to show that query on Java it does not work. I'm new to this, and using classicmodels Db. The following query that worked on workbench:

select c.customerNumber, c.customerName,
o.orderNumber,
d.productCode, d.quantityOrdered, d.priceEach, (d.quantityOrdered * d.priceEach) as totalPrice,
e.employeeNumber, e.lastName, ((d.quantityOrdered * d.priceEach)*0.01) as commission
from customers as c inner join orders as o on c.customerNumber=o.customerNumber inner join 
orderdetails as d on o.orderNumber=d.orderNumber
inner join employees as e on c.salesRepEmployeeNumber=e.employeeNumber group by productCode;

'486', 'Motor Mint Distributors Inc.', '10109', 'S18_1129', '26', '117.48', '3054.48', '1323', 'Vanauf', '30.5448'

Here is my Java code:

public void query() {

    try {
        Class.forName("com.mysql.jdbc.Driver");

        conn = DriverManager.getConnection(urlConn, user, passWord);
        pdState = conn.prepareStatement("SELECT c.customerNumber, c.customerName,o.orderNumber,"
                + " d.productCode, d.quantityOrdered, d.priceEach,(d.quantityOrdered * d.priceEach) as totalPrice,"
                + " e.employeeNumber, e.lastName,((d.quantityOrdered * d.priceEach)*0.01) as commission"
                + " FROM customers as c inner join orders as o on c.customerNumber=o.customerNumber"
                + " inner join orderdetails as d on o.orderNumber=d.orderNumber"
                + " inner join employees as e on c.salesRepEmployeeNumber=e.employeeNumbergroup by productCode");

        rSet = pdState.executeQuery();

        ResultSetMetaData rsmd = rSet.getMetaData();
        c = rsmd.getColumnCount();

        DefaultTableModel dtModel = (DefaultTableModel) tblQuery.getModel();
        dtModel.setRowCount(0);

        while (rSet.next()) {
            @SuppressWarnings("UseOfObsoleteCollectionType")
            Vector vector = new Vector();
            for (int i = 1; i <= c; i++) {
                vector.add(rSet.getString("customerNumber"));
                vector.add(rSet.getString("customerName"));
                vector.add(rSet.getString("orderNumber"));
                vector.add(rSet.getString("productCode"));
                vector.add(rSet.getString("quantityOrdered"));
                vector.add(rSet.getString("priceEach"));
                vector.add(rSet.getString("totalPrice"));
                vector.add(rSet.getString("employeeNumber"));
                vector.add(rSet.getString("lastName"));
                vector.add(rSet.getString("commission"));
            }//end of for loop

            dtModel.addRow(vector);

        }//end of while loop
    } catch (ClassNotFoundException | SQLException e) {
        e.getMessage();
    }//end of try and catch block
}//end of query

Answer 1

The problem here is the group by clause. You've grouped on one field, and failed to ensure all the other fields are either uniquely determined by that field, or grouped functions. Remove the group by productCode and everything should work.

I think the reason it "worked" in MySQL workbench is probably that there is an option you can set (but probably should not) that allows improper grouped fields to "work" (I think by just picking one of many values).

As an example of a query that might work, the following should report the commission each employee has earned by product sold. Since the customer is irrelevant to that information, that table wasn't queried.

select d.productCode, e.employeeNumber, e.lastName, 
       sum((d.quantityOrdered * d.priceEach)*0.01) as commission
from orders as o
inner join orderdetails as d on o.orderNumber=d.orderNumber
inner join employees as e on c.salesRepEmployeeNumber=e.employeeNumber
group by productCode, employeeNumber;