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SQLite DELETE query won't delete from database

Here's my code for the addStudent:
#FXML
private void addStudent(ActionEvent event) {
// sql query to insert data into students at ID, first name, last name, email and DOB
String sqlInsert = "INSERT INTO students(id,fname,lname,email,DOB) VALUES (?,?,?,?,?)";
try {
Connection conn = dbConnection.getConnection();
PreparedStatement stmt = conn.prepareStatement(sqlInsert);
// add the data in the right column
stmt.setString(1, this.id.getText());
stmt.setString(2, this.firstname.getText());
stmt.setString(3, this.lastname.getText());
stmt.setString(4, this.email.getText());
stmt.setString(5, this.dob.getEditor().getText());
stmt.execute();
conn.close();
} catch(SQLException ex) {
ex.printStackTrace();
}
}
And here's my code for removeStudent:
#FXML
private void removeStudent(ActionEvent event) {
try {
// sql query to delete data from the database
String sqlRemove = "DELETE FROM students WHERE id = ?";
// open a connection to the database and use PreparedStatement to
// initialize the query.
Connection conn = dbConnection.getConnection();
PreparedStatement delete = conn.prepareStatement(sqlRemove);
// information needed to delete the row
delete.setString(1, selectStudent());
// execute and delete
delete.executeUpdate();
// close the connection
conn.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
// update table after deleting
loadStudentData(event);
}
The picture above is the view of my table. I hit LoadData and my table values show up. I want to be able to click on a row(student) and hit Delete Student to remove it.
Helper method for removeStudent:
private String selectStudent() {
String result = "";
try {
String sqlSelect = "SELECT id FROM students";
Connection conn = dbConnection.getConnection();
ResultSet rs = conn.createStatement().executeQuery(sqlSelect);
result = rs.getString(1);
conn.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
return result;
}
I'm pretty sure it has to do with when I "click" on a row, the id value for that isn't being held anywhere so when I hit "Delete" nothing is being given for it to Delete.
I don't know. Any advice would be awesome. :D
First edit: nothing is assigned to delete.setString(1, this.id.getText()). When I click on the row and hit delete, nothing is happening because there's nothing being assigned to id when I click on the row. The query string DOES work however when I physically give it an ID to delete. Also verified that the button does work; it prints out a lovely message for me with a good ol' System.out.println("expletive");
Second edit: Ok, so I updated the removeStudent code and now all I get is the string "null" returned. Nothing deletes. Nothing updates. Nothing is happening except I get "null" in the console.
Third edit: Getting closer! With the realization that the removeStudent isn't being given an ID to delete, I decided to create a private helper method that will do a SELECT query. Now, when I hit delete, it'll delete....but from the top, and not at where I want it selected. The code is above.
Fourth edit: Getting even closer! So, I figured out how to capture the row I click on within the table and I can delete......however, because of my sqlRemove command, I'm deleting by id so if I click on a row with index 3, then ONLY the row within the table that has an id of 3 will be deleted, nothing else. I gotta re-write how the sqlRemove command is worded.

I fixed it:
private String selectStudent() {
// initial value for result to return
String result = "";
// grab the index of the row selected on the table
int initial = studenttable.getSelectionModel().getSelectedIndex();
try {
// SELECT query to execute
String sqlSelect = "SELECT id FROM students";
Connection conn = dbConnection.getConnection();
ResultSet rs = conn.createStatement().executeQuery(sqlSelect);
// while there's a next row
while(rs.next()) {
// set temp to equal the id rs.next() is currently on
String temp = rs.getString("id");
// get the row id - 1 since we start at 0
int temp1 = rs.getRow() - 1;
// if temp1 is equal to the index we selected
if(temp1 == initial) {
// make it equal to result
result = temp;
}
}
// close the connection
conn.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
// return the row to delete
return result;
}
What's going on is in the comments. I finally figured out how to pass the value from a selected row and compare it to a row. Once I get the correct row to pass, I give it to the delete function to remove.
After a day in a half.............but I love it, so. Yeah.

Java-Output all the columns and rows of a ResultSet

ta.setText is a TextArea where I want to show all my data from the database, after a button click. But with rs.get("name") I just output one value and it is always the last. How can I print out the whole table from the database, so all the information which are stored there?
try { String newquery = "SELECT * FROM kunden";
java.sql.PreparedStatement ps = con.prepareStatement(newquery);
rs = ps.executeQuery(newquery);
while (rs.next()){
ta.setText(rs.getString("name"));
ta.setText(rs.getString("nachname"));
}
}// try
catch(Exception e1) {
JOptionPane.showMessageDialog(null, "fail");
}
}//actionperformed

Either you build a string an then set that string using setText()
StringBuilder builder = new StringBuilder();
while (rs.next()) {
builder.append(rs.getString(“name”));
builder.append(“ “);
builder.append(rs.getString(“nachname”));
builder.append(“\n“);
}
ta.setText(builder.toString());
Or you use the append method that exists for TextArea
while (rs.next()) {
ta.append(rs.getString(“name”));
ta.append(“ “);
ta.append(rs.getString(“nachname”));
ta.append(“\n“);
}

Java ResultSet next() and previous() buttons are not working

Hey guys I'm trying to scroll through the rows in my database. For some reason my previous and next buttons are not working. Next button displays just first row and previous button doesn't display anything. My first and last buttons are working.
private void previousbtnActionPerformed(java.awt.event.ActionEvent evt) {
try
{
con = DriverManager.getConnection(CONN_STRING, USERNAME, PASSWORD);
Statement st = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
ResultSet rs = st.executeQuery("SELECT * FROM EMPLOYEE");
if (rs.previous())
{
str1 = rs.getString("emp_id");
emp_id.setText(str1);
str2 = rs.getString("emp_fname");
first_name.setText(str2);
str3 = rs.getString("emp_lname");
last_name.setText(str3);
}
else
{
rs.next();
}
con.close();
}
catch (SQLException err)
{
JOptionPane.showMessageDialog(EmployeeGUI.this, err.getMessage());
}
}
private void nextbtnActionPerformed(java.awt.event.ActionEvent evt) {
try
{
con = DriverManager.getConnection(CONN_STRING, USERNAME, PASSWORD);
Statement st = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_UPDATABLE);
ResultSet rs = st.executeQuery("select * from employee");
if (rs.next())
{
str1 = rs.getString("emp_id");
emp_id.setText(str1);
str2 = rs.getString("emp_fname");
first_name.setText(str2);
str3 = rs.getString("emp_lname");
last_name.setText(str3);
}
else
{
rs.previous();
}
}
catch (SQLException err)
{
JOptionPane.showMessageDialog(EmployeeGUI.this, err.getMessage());
}
}

Here's the javadoc for ResultSet and this is what it says:
A ResultSet object maintains a cursor pointing to its current row of
data. Initially the cursor is positioned before the first row. The
next method moves the cursor to the next row, and because it returns
false when there are no more rows in the ResultSet object, it can be
used in a while loop to iterate through the result set.
So, when you get the ResultSet object, it will always be placed before the previous row and hence, previous() will always return false.
Assuming you are trying to implement Pagination with these buttons, I would recommend having a look at MySQL SELECT documentation and use limit to get the rows, e.g.:
SELECT * FROM tbl LIMIT 5,10; # Retrieve rows 6-15
You can use it with LIMIT i, 1 where i will increment with each click of next and decrement with each click of previous.

Retrieving data from database and increment by one

I am trying to retrieve a data (ID No.) from a database (MySQL) and add it by one. However, when I try to put this code below, when I try to build it, the form doesn't show up. But when I try to remove the Connection cn line, the form with finally show up. I had another project with this code it it worked perfectly fine. I'm not sure why its not working on this one.
public Abstract() throws Exception {
Connection cn = DriverManager.getConnection("jdbc:mysql://localhost:3306/user?zeroDateTimeBehavior=convertToNull","root","");
initComponents();
Statement st = null;
ResultSet rs;
try {
String sql = "SELECT ID from bidding_abstractofprices";
st = cn.prepareStatement(sql);
rs = st.executeQuery(sql);
while(rs.next()){
int id = Integer.parseInt(rs.getString("ID")) + 1;
lblTransacID.setText(String.valueOf(id));
}
}catch (Exception ex){
}
}

What it looks like you are trying to do is to get the ID field value from the last record contained within the bidding_abstractofprices Table contained within your Database and then increment that ID value by one (please correct me if I'm wrong). I don't care why but I can easily assume. Here is how I might do it:
public Abstract() throws Exception {
// Allow all your components to initialize first.
initComponents();
Connection cn = DriverManager.getConnection("jdbc:mysql://localhost:3306/user?zeroDateTimeBehavior=convertToNull","root","");
Statement st = null;
ResultSet rs;
try {
String sql = "SELECT * FROM bidding_abstractofprices ORDER BY ID DESC LIMIT 1;";
st = cn.prepareStatement(sql);
rs = st.executeQuery(sql);
int id = 0;
while(rs.next()){
id = rs.getInt("ID") + 1;
}
lblTransacID.setText(String.valueOf(id));
rs.close();
st.close();
cn.close();
} catch (SQLException ex) {
ex.printStackTrace();
}
}

A lock could not obtained within the time requested issue

The title is the error I'm getting, when I click load my program freezes. I assume it's because I'm doing a statement inside a statement, but from what I see it's the only solution to my issue. By loading, I want to just repopulate the list of patients, but to do so I need to do their conditions also. The code works, the bottom method is what I'm trying to fix. I think the issue is that I have 2 statements open but I am not sure.
load:
public void DatabaseLoad()
{
try
{
String Name = "Wayne";
String Pass= "Wayne";
String Host = "jdbc:derby://localhost:1527/Patients";
Connection con = DriverManager.getConnection( Host,Name, Pass);
PatientList.clear();
Statement stmt8 = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_UPDATABLE);
String SQL8 = "SELECT * FROM PATIENTS";
ResultSet rs8 = stmt8.executeQuery( SQL8 );
ArrayList<PatientCondition> PatientConditions1 = new ArrayList();
while(rs8.next())
{
PatientConditions1 = LoadPatientConditions();
}
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_UPDATABLE);
String SQL = "SELECT * FROM PATIENTS";
ResultSet rs = stmt.executeQuery( SQL );
while(rs.next())
{
int id = (rs.getInt("ID"));
String name = (rs.getString("NAME"));
int age = (rs.getInt("AGE"));
String address = (rs.getString("ADDRESS"));
String sex = (rs.getString("SEX"));
String phone = (rs.getString("PHONE"));
Patient p = new Patient(id, name, age, address, sex, phone,
PatientConditions1);
PatientList.add(p);
}
UpdateTable();
UpdateAllViews();
DefaultListModel PatientListModel = new DefaultListModel();
for (Patient s : PatientList) {
PatientListModel.addElement(s.getAccountNumber() + "-" + s.getName());
}
PatientJList.setModel(PatientListModel);
}
catch(SQLException err)
{
System.out.println(err.getMessage());
}
}
This is the method that returns the ArrayList of patient conditions
public ArrayList LoadPatientConditions()
{
ArrayList<PatientCondition> PatientConditionsTemp = new ArrayList();
try
{
String Name = "Wayne";
String Pass= "Wayne";
String Host = "jdbc:derby://localhost:1527/Patients";
Connection con = DriverManager.getConnection( Host,Name, Pass);
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_UPDATABLE);
String SQL = "SELECT * FROM PATIENTCONDITIONS";
ResultSet rs5 = stmt.executeQuery( SQL );
int e = 0;
while(rs5.next())
{
e++;
String ConName = (rs5.getString("CONDITION"));
PatientCondition k = new PatientCondition(e,ConName);
PatientConditionsTemp.add(k);
}
}
catch(SQLException err)
{
System.out.println(err.getMessage());
}
return PatientConditionsTemp;
}

I had a similar problem.
I was connecting to derby db hosted on local server.
I created 2 simultaneous connections:
With squirrel
With ij tool
When a connection makes a modification on a table, it first gets a lock for the particular table.
This lock is released by the connection only after committing the transaction.
Thus if the second connection tries to read/write the same table, a msg prompts saying:
ERROR 40XL1: A lock could not be obtained within the time requested
To fix this, the connection which modified the table has to commit its transaction.
Hope this helps !

Here is a good place to start: http://wiki.apache.org/db-derby/LockDebugging

You need to close your statement and result set as well so that when you restart your program they won't be open. Add stmt.close(); and rs.close(); at the end of your lines of code within the try and catch statement.

Why could you not use the same connection object to do both the queries?
Like pass that connection object to the LoadPatientConditions() as a parameter and use it there.