选择 Query 并将出现在 Netbeans & mysql 中的组合框

Question

I got problem on this code:
String charitysql = "SELECT wardName, charityRoomID FROM tbl_charityward,tbl_charityroom2
WHERE tbl_charityward.charityWardID = tbl_charityroom2.charityWardID";


 try { 

        pst = conn.prepareStatement(charitysql);
        rs = pst.executeQuery();

            while (rs.next()) {
                String wardname = rs.getString("wardName");
                cb_ward2.addItem(wardname);
                String roomid = rs.getString("charityRoomID");
                cb_room2.addItem(roomid);                    

            }

        }
        catch(Exception e) {
            JOptionPane.showMessageDialog(null, e);
        }

this is my tables structure:
tbl_charityward
charityWardID int NOT NULL AUTO_INCREMENT,
wardName varchar(20),
status varchar(20),
PRIMARY KEY (charityWardID)

tbl_charityRoom2
charityRoomID INT NOT NULL AUTO_INCREMENT,
status varchar(20),
charityWardID int,
PRIMARY KEY (charityRoomID, charityWardID),
FOREIGN KEY (charityWardID) REFERENCES tbl_charityward (charityWardID)

this is my tables with values:
tbl_charityward
+-------------+----------+--------+
|charityWardID| wardName | status |
+-------------+----------+--------+
|......1......| Surgical |..Open..|
|......2......| .Obygine |..Open..|
|......3......| Pediatric|..Open..|
+-------------+----------+--------+


tbl_charityroom2
+-------------+--------+-------------+
|charityRoomID| status |charityWardID|
+-------------+--------+-------------+
|......1......|..Open..|......1......|
|......2......|..Open..|......1......|
|......3......|..Open..|......2......|
+-------------+--------+-------------+


I have 2 comboBox:
cb_ward2 = which contains wardName
cb_room2 = which contains CharityRoomID

If I select a wardName from cb_ward2 , then the cb_room2 will show the corresponding charityRoomID.

example:
I select Surgical and the charityRoomID = 1, 2 will appear on cb_room2 ,
and when i select Obygine , the charityRoomID = 3 will only appear on cb_room2 ,
but when i select Pediatric , no charityRoomID will appear on cb_room2

I am using Netbeans and MYSQL EDIT :

---

I am using Netbeans and MYSQL EDIT :

 import java.sql.*;<br> import javax.swing.*;<br> public class addBed extends javax.swing.JFrame { Connection conn = null; ResultSet rs = null; PreparedStatement pst = null; /** * Creates new form addBed */ public addBed() { initComponents(); } void loadcombo() { try { String charitysql = "SELECT wardName, charityRoomID FROM tbl_charityward, tbl_charityroom2 WHERE tbl_charityward.charityWardID = ?"; pst = conn.prepareStatement(charitysql); pst.setInt(1,tbl_charityroom2.charityWardID); rs = pst.executeQuery(); while (rs.next()) { cb_ward2.addItem(rs.getString(1)); cb_room2.addItem(rs.getString(2)); } } catch(Exception e) { JOptionPane.showMessageDialog(null, e); } } private void formWindowOpened(java.awt.event.WindowEvent evt) { conn = myconn.ConnectDb(); loadcombo(); } private void btn_add2ActionPerformed(java.awt.event.ActionEvent evt) { }

Answer 1

The way you are using is not the proper way of using PreparedStatement

Do like this

String charitysql = "SELECT wardName, charityRoomID FROM tbl_charityward,tbl_charityroom2 
WHERE tbl_charityward.charityWardID = ?";
pst = conn.prepareStatement(charitysql);
pst.setInt(1,tbl_charityroom2.charityWardID);
rs = pst.executeQuery();

Answer 2

As your basic requirement is to show data into two ComboBoxes , you can do it as:

You can use a loadcombo() to load your cb_ward2 combobox with database values.

void loadcombo() {
    try
    {
     Connection conn=null;
 PreparedStatement pst=null;
 ResultSet rs=null;
// Your database connections 

     String charitysql = "SELECT wardName FROM tbl_charityward";
     pst = conn.prepareStatement(charitysql);
     rs = pst.executeQuery();
    while(rs.next()){                            
        cb_ward2.addItem(rs.getString(1));
    }
    con.close();
    }
    catch(Exception e)
    {
        System.out.println("Error"+e);
    }    
}

Now you can use ActionListener on cb_ward2 as:

cb_ward2.addActionListener(new ActionListener(){


    public void actionPerformed(ActionEvent ae){
        try
    {
        Connection con=null;
        PreparedStatement pst=null,pst1=null;
        ResultSet rs=null,rs1=null;
    //your database connection
                Object name=cb_ward2.getSelectedItem();
                    pst=con.preparedStatement("select charityWardID from tbl_charityward where wardName=?");
                pst.setObject(1,name);
                    rs= pst.executeQuery();
        if(rs.next())
        {
                      pst1=con.preparedStatement("select charityRoomID from tbl_charityroom2 where charityWardID=?");
                      pst1.setInt(1,rs.getInt(1));
                      rs1=pst1.executeQuery();
                      while(rs1.next()){
                      cb_room2.addItem(rs1.getInt(1));
                      }
            }
                con.close();
    }
    catch(Exception e)
    {
        System.out.println("GG"+e);
    }

    }


    });

Answer 3

try using an arrayList !! it will give you a push like effect

something like this

    ArrayList<String> categories = new ArrayList<>();
    Connection conn = null;
    Statement stmt = null;
    ResultSet rs = null;
    try {
        System.out.println("\ntrying connection");
        conn = DriverManager.getConnection("jdbc:mysql://localhost/products?user=root&password=");
        stmt = conn.createStatement();
        rs = stmt.executeQuery("SELECT DISTINCT categorie FROM product");
        while (rs.next()) {
            categories.add(rs.getString(1));
        }
        for (String item : categories) {
            ComboBoxCategorie.addItem(item);
        }

    } catch (SQLException ex) {
        System.out.println("SQLException: " + ex.getMessage());
        System.out.println("SQLState: " + ex.getSQLState());
        System.out.println("VendorError: " + ex.getErrorCode());
    } finally {
        if (stmt != null) {
            try {
                stmt.close();
            } catch (SQLException sqlEx) {
            } // ignore
            stmt = null;
        }
    }

you can ignore the catch and finally clause!! just close the stmt