java - 如何在 Java 中的结果集中包含多个 Select 语句

Question

我当前遇到的问题是我想选择一列并对值求和。然后我想总结同一个表中的另一列。目的是获取这两列的总和并减去它们以获得输出。我的用途是利用假期。员工每周都会获得休假时间。然后，当使用它们时，它们位于不同的列中。我需要计算出他们可以使用的剩余假期总数。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

这是否可以在一个结果集中完成？或者我是否需要制作单独的结果集来执行此操作。

Answer 1

您的 sql 有一些问题。首先，不能用逗号分隔多个选择。相反，您应该有一个包含多列的选择。其次，您不应该按 Vacation_gained、vacation_used 进行分组，因为您在聚合函数中使用这些字段。 sql 应如下所示:

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

或者，如果您只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:

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