如何在 Java 的结果集中有多个 Select 语句

Question

我目前遇到的问题是我想选择一列并对值求和。然后我想总结同一张表中的另一列。目标是取这两个相加的列并将它们相减以获得输出。我的用途是休假。每周，员工都会获得数小时的假期。然后，当它们被使用时，它们位于不同的列中。我需要算出他们可以使用的假期总数。 这就是我所拥有的：

try
    {
         //Getting Information FROM EMPLOYEE_TIME_LOG for Vacation
            Statement vacationLogstmt = dbConn.createStatement();
            ResultSet vacationLogSet = vacationLogstmt.executeQuery(
                         "(SELECT SUM(vacation_gained) FROM employee_time_log WHERE employee_id_number = " +userInputIdNumber + "), " +
                         "(SELECT SUM(vacation_used) FROM employee_time_log WHERE employee_id_number = " +userInputIdNumber + "), " +
                     "GROUP BY vacation_gained, vacation_used");

           vacationLogSet.next();
           String strVacationEarned = vacationLogSet.getString(1);
           String strVacationUsed = vacationLogSet.getString(2);
           Double vacationEarned = Double.parseDouble(strVacationEarned);
           Double vacationUsed = Double.parseDouble(strVacationUsed);
           Double totalVacation = (vacationEarned - vacationUsed); 
           String strTotalVacation =Double.toString(totalVacation);
           txtVacationTotal.setText(strTotalVacation);
    }
    catch (SQLException e)
    {
          //throw new JboException(e);
            System.err.println(e);
            String connectionError = "Problem with the database, please contact MIS.";
            JOptionPane.showMessageDialog(new JFrame(), connectionError, "Database Error",JOptionPane.ERROR_MESSAGE);
            txtUserSignIn.setText("");
            txtUserSignIn.requestFocus();      
    }

我收到一个错误： java.sql.SQLSyntaxErrorException: ORA-00933: SQL 命令未正确结束

这甚至可以在一个结果集中完成吗？还是我只需要制作单独的结果集来做到这一点。

Answer 1

您的 sql 存在一些问题。首先，您不能使用逗号分隔多个选择。相反，您应该选择一个包含多列的选项。其次，您不应该按vacation_gained、vacation_used 分组，因为您在聚合函数中使用这些字段。 sql应该如下：

"(SELECT SUM(vacation_gained), SUM(vacation_used) FROM employee_time_log WHERE employee_id_number = " + userInputIdNumber + ")";

或者，如果您只是对剩余的假期时间感兴趣，您也可以将数学作为查询的一部分进行：

"(SELECT SUM(vacation_gained) - SUM(vacation_used) as total_vacation FROM employee_time_log WHERE employee_id_number = " + userInputIdNumber + ")";