java - 为什么 select 语句总是返回最后插入的值？

Question

当我尝试使用准备好的语句选择记录时，它总是给出我最近添加的最后插入的值。

首先我做的是在第一个表中搜索记录。如果记录存在，外键表将填充值。我的主键和外键表运行良好。这些值适本地填充到相应的组件中，但它没有给我正确的值。有什么帮助吗？

这是引用第二个表的外键表的主键表。

选择查询:

String searchSECTIONNAME = "SELECT * FROM allsections_list WHERE SECTION_NAME = ?";//1st Select Statement

String searchSECTIONSETTINGS = "SELECT allsections_list.`SECTION_ID`, allsections_settings.ADVISER_ASSIGNED, allsections_settings.SECTION_POPULIMIT,\n" +
    "allsections_settings.ROOM_ASSGN, allsections_settings.YRLEVEL_ASSGN, allsections_settings.SCHOOL_YEAR, allsections_settings.SESSION_ASSIGNED\n" +
    "FROM allsections_list\n" +
    "RIGHT JOIN allsections_settings\n" +
    "ON allsections_list.`SECTION_ID`=allsections_settings.`SECTION_ID`";//2nd Select Statement

所以我在这里所做的是使用右连接将SECTION_NAME列连接到外键表。如果记录存在，它将连接两个表。

代码:

 private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    String searchSection = Section_SearchSection_Textfield.getText();


    try (Connection myConn = DBUtil.connect();
         PreparedStatement myFirstPs = myConn.prepareStatement(searchSECTIONNAME);)
        {
            myFirstPs.setString(1, searchSection);

         try (ResultSet myFirstRs = myFirstPs.executeQuery())
         {
             int resultCounter = 0;
             while (myFirstRs.next())
             {
                 String mySectionName = myFirstRs.getString(2);//Get the value of SECTION_NAME
                 Section_SectionName_TextField.setText(mySectionName);
                 Section_SectionName_TextField.setEnabled(true);

                 try (PreparedStatement mySecondPs = myConn.prepareStatement(searchSECTIONSETTINGS))
                 {
                    try (ResultSet mySecondRs = mySecondPs.executeQuery())
                    {
                        while (mySecondRs.next())
                        {
                            String myAdviserAssigned = mySecondRs.getString(2);
                            Section_Student_Limit_ComboBox1.setSelectedItem(myAdviserAssigned);
                            Section_Student_Limit_ComboBox1.setEnabled(true);

                            String mySectionPopulation = mySecondRs.getString(3);
                            Section_Student_Limit_ComboBox.setSelectedItem(mySectionPopulation);
                            Section_Student_Limit_ComboBox.setEnabled(true);

                            String myRoomAssigned = mySecondRs.getString(4);
                            Section_Room_Assignment_ComboBox.setSelectedItem(myRoomAssigned);
                            Section_Room_Assignment_ComboBox.setEnabled(true);

                            String myYearLevelAssigned = mySecondRs.getString(5);
                            Section_Session_Level_ComboBox.setSelectedItem(myYearLevelAssigned);
                            Section_Session_Level_ComboBox.setEnabled(true);

                            String mySchoolYear = mySecondRs.getString(6);
                            Section_SchooYear_ComboBox.setSelectedItem(mySchoolYear);
                            Section_SchooYear_ComboBox.setEnabled(true);

                            String mySessionAssigned = mySecondRs.getString(7);
                            Section_Session_Settings_ComboBox.setSelectedItem(mySessionAssigned);
                            Section_Session_Settings_ComboBox.setEnabled(true);

                            resultCounter++;

                        }//end of loop mySecondRs (ResultSet)
                    }//end of try mySecondRs (ResultSet)
                 }//end of try mySecondPs (PreparedStatement)

             }//end of loop myFirstRs (ResultSet)
             if (resultCounter == 1)//If exist
             {
                 JOptionPane.showMessageDialog(null, "Data Found");
             }
             else//If not exist
                 JOptionPane.showMessageDialog(null, "No Data Found");
         }//end of try myFirstRs (ResultSet)

    }//end of try myFirstPs (PreparedStatement)

        catch (SQLException e) 
        { 
            DBUtil.processException(e);
        }//end of catch
}

正如你在这里看到的。在我的第一个 ResultSet myFirstRs 中，当我搜索现有 SECTION_NAME 时，将填充外键值。如果我的循环中有什么东西纠正了我。提前致谢!

更新!

我在第二个选择查询中添加了 ORDER BY 子句。因为如果没有这个，数据库将返回它想要的内容，所以我所做的就是修改查询并添加 ORDER BY 子句，如下所示:

String searchSECTIONSETTINGS = "SELECT allsections_list.`SECTION_ID`, allsections_settings.ADVISER_ASSIGNED, allsections_settings.SECTION_POPULIMIT,\n" +
    "allsections_settings.ROOM_ASSGN, allsections_settings.YRLEVEL_ASSGN, allsections_settings.SCHOOL_YEAR, allsections_settings.SESSION_ASSIGNED\n" +
    "FROM allsections_list\n" +
    "RIGHT JOIN allsections_settings\n" +
    "ON allsections_list.`SECTION_ID` = allsections_settings.`SECTION_ID`" +
    "ORDER BY allsections_list.SECTION_ID";

当我运行项目时仍然给我错误的值。我尝试在 NetBeans 查询中运行此查询，并按 ASC 顺序给我一个值。

Answer 1

我刚刚找到了一个最简单的解决方案。我使用右连接连接了两个表。

private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    String searchSection = Section_SearchSection_Textfield.getText().replace("!", "!!").replace("%", "!%").replace("_", "!_")
   .replace("[", "![");

    String searchSECTIONSETTINGS = "SELECT allsections_list.SECTION_ID as 'ID', allsections_list.SECTION_NAME as 'Section Name', allsections_settings.ADVISER_ASSIGNED as 'Adviser', allsections_settings.SECTION_POPULIMIT as 'Population',\n" +
    "allsections_settings.ROOM_ASSGN as 'Room', allsections_settings.YRLEVEL_ASSGN as 'Year Level', allsections_settings.SCHOOL_YEAR as 'School Year', allsections_settings.SESSION_ASSIGNED as 'Session'\n" +
    "FROM allsections_list\n" +
    "RIGHT JOIN allsections_settings\n" +
    "ON allsections_list.SECTION_ID = allsections_settings.SECTION_ID\n" +
    "WHERE SECTION_NAME LIKE ? ESCAPE '!'\n" +
    "ORDER BY allsections_list.SECTION_ID";

    if (searchSection.isEmpty())
    {
        JOptionPane.showMessageDialog(null, "Please fill up this fields");
    }
    else 
        try (Connection myConn = DBUtil.connect();
         PreparedStatement myFirstPs = myConn.prepareStatement(searchSECTIONSETTINGS);)
        {
              myFirstPs.setString(1, "%" +searchSection +"%");
         try (ResultSet myFirstRs = myFirstPs.executeQuery())
         {
             int resultCounter = 0;
             while (myFirstRs.next())
             {
                 String name = myFirstRs.getString(2);
                 sectionJTable.setModel(DbUtils.resultSetToTableModel(myFirstRs));
                 resultCounter++;
             }//end of loop myFirstRs (ResultSet)

             if (resultCounter > 0)//If exist
             {
                 JOptionPane.showMessageDialog(null, "Data Found");
             }
             else//If not exist
                 JOptionPane.showMessageDialog(null, "No Data Found");
         }//end of try myFirstRs (ResultSet)

    }//end of try myFirstPs (PreparedStatement)

        catch (SQLException e) 
        { 
            DBUtil.processException(e);
        }//end of catch
}