private void getRegisteredCoursesActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_getRegisteredCoursesActionPerformed
String query = "select * from register where grade IS NULL AND studentID = " + studentIDTextField.getText();
ResultSet rs = DatabaseHandler.getInstance().executeQueryAndReturnResultSet(query);
DefaultTableModel m = (DefaultTableModel)registeredCoursesTable.getModel();
while(m.getRowCount() != 0){
m.removeRow(0);
}
try{
while(rs.next()){
m.addRow(new Object[] {rs.getString("levelName"), rs.getString("courseName"), rs.getString("semester"), rs.getString("year")});
}