Mysql 数据库表中返回0的列的总和

我正在使用mySql数据库

我创建了一个方法来计算列的和。它工作得很好

public int calculate(String department) {
    int sum = 0;
    try {
        BaseDao baseDao = new BaseDao();
        Connection connection = baseDao.getConnection();
        String query = "select sum(Allocation) from test.Employee where Department=?";
        PreparedStatement preparedStatement = connection.prepareStatement(query);
        preparedStatement.setString(1, department);
        ResultSet resultSet = preparedStatement.executeQuery();
        while (resultSet.next()) {
            int c=resultSet.getInt(1);
            sum = sum+c;
        }
        System.out.println(sum);
        }catch(Exception e) {
        e.printStackTrace();
    }
    return sum; 
}

我还创建了另一个方法，在这个方法中，我计算列的和，并且我提到了两个条件，但它不起作用。它显示总和为0

    public int calculate2(String managerId, String managerId2) {
    int sum = 0;
    try {
        BaseDao baseDao = new BaseDao();
        Connection connection = baseDao.getConnection();
        String query = "select sum(Allocation) from test.Employee where EmployeeId=? and Manager=?";
        PreparedStatement preparedStatement = connection.prepareStatement(query);
        preparedStatement.setString(1, managerId);
        preparedStatement.setString(2, managerId2);
        ResultSet resultSet = preparedStatement.executeQuery();
        while (resultSet.next()) {
            int c = resultSet.getInt(1);
            sum=sum+c;
        }
        System.out.println(sum);
        }catch(Exception e) {
        e.printStackTrace();
    }
    return sum;
}

这是错误日志

Oct 03, 2013 9:06:22 PM org.apache.catalina.core.StandardContext reload
INFO: Reloading Context with name [/SavvisProject] has started
Oct 03, 2013 9:06:22 PM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
SEVERE: The web application [/SavvisProject] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
Oct 03, 2013 9:06:23 PM org.apache.catalina.core.StandardContext reload
INFO: Reloading Context with name [/SavvisProject] is completed

---

您是否尝试输入您试图直接运行到mySql的查询？可能总和实际上是0。您确定数据库中有用于测试EmployeeID和Manager的值的数据吗。另外，假设EmployeeID是Employee表的主键，为什么还需要在manager上进行筛选（如果只有一行包含任何给定的EmployeeID，为什么需要聚合结果）？很抱歉，实际上我需要EmployeeID=？或者经理=？现在，我得到了我的答案。@spydon你是对的。该查询的结果为0。