Deleteing data from database based on a jcomboBox throws an error - java

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt)
{
Connection conn=DbCon.conDB();
//String Mname =jComboBox1.getSelectedItem().toString();
String sql="delete Name from nowshowingmovie where Name = '"+jComboBox1.getSelectedItem().toString()+"'";
try{
pst=conn.prepareStatement(sql);
// pst.executeQuery();
pst.executeUpdate(sql);
JOptionPane.showMessageDialog(null,"Movie Deleted Sucessfully");
}
catch(SQLException e)
{
JOptionPane.showMessageDialog(null, e);
}
}


2 issues:
In general the syntax for DELETE is
String sql = "delete from nowshowingmovie where Name = '"+jComboBox1.getSelectedItem().toString()+"'";
PreparedStatement doesn't use the SQL String, i.e. just use pst.executeUpdate()
Side note: Since you're already using a PreparedStatement you can use a placeholder to avoid SQL injection attacks rather than using String concatenation.
String sql = "delete from nowshowingmovie where Name = ?";
pst.setString(1, jComboBox1.getSelectedItem().toString());
pst.executeUpdate();

Related

java.sql.SQLSyntaxErrorException with Prepared Statements

I just started learning about MySQL and I am now trying to learn prepared statements. When I uses them, I get this error java.sql.SQLSyntaxErrorException. Can someone tell me where am I getting the syntax wrong? Thanks. Here is my code:
public class DBConnector {
private Statement statement;
private ResultSet result;
private PreparedStatement preparedStatement;
public void createDB() {
try {
sql = "CREATE DATABASE IF NOT EXISTS ?";
tableName = "test_name";
preparedStatement = connection.prepareStatement(sql);
preparedStatement.setString(1, tableName);
int myResult = preparedStatement.executeUpdate();
if(myResult == 1){
System.out.println("Database successfully created.");
}else{
System.out.println("Database with that name already exists. Please try again with different name.");
createDB();
}
}catch (SQLException e) {
System.out.println("Database creation failed.");
e.printStackTrace();
}
}
}

We can't bind Database names in Query parameters.
Statement stmt=con.createStatement();
int rs=stmt.executeUpdate("CREATE DATABASE dbname");
Try in this way, Database will create.

Getting Java mysql SQL Syntax error but my query seems normal

I am developing a simple java mysql based application and during data insertion into the database I'm getting an SQL error mentioned below.
Here is my code:
public DBConnection() {
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/myDatabase?useUnicode=true&useLegacyDatetimeCode=false&serverTimezone=Turkey", "root", "");
st = con.createStatement();
System.out.println("CONNECTED!");
} catch (Exception e) {
System.out.println("Error : " + e);
}
}
public void addCustomer(String name, String surname, String company, String adress, String adressTwo){
String addQuery = "insert into musteri (name,surname,company,adress,adressTwo) values (?,?,?,?,?)" ;
try {
st.executeUpdate(addQuery);
System.out.println("Data Added");
} catch (Exception e) {
System.out.println("Error occured when adding value to database : " + e );
}
}
Here is my java main method that add's the data:
public static void main(String[] args) {
// TODO code application logic here
Customers c1 = new Customers();
c1.setIsim("test");
c1.setSoyisim("test");
c1.setSirket("test");
c1.setAdres("test");
c1.setIletisim("test");
DBConnection db = new DBConnection();
db.addCustomer(c1.isim, c1.soyisim, c1.sirket, c1.adres, c1.iletisim);
}
The error I'm getting is:
Error occured when adding value to database : java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ''insert into musteri (ad,soyad,sirket,adres,iletisim) values (?,?,?,?,?)'' at line 1

You are mixing statements with prepared statements. You should use a prepared statement and set the values to it:
public void addCustomer(String name, String surname, String company, String address, String adressTwo) {
String addQuery = "insert into musteri (name, surname, company, adress, adressTwo) values (?,?,?,?,?)" ;
// Shown here for simplicitly.
// The query could be prepared once and stored in a data member
try (PreparedStatement ps = con.prepareStatement(addQuery)) {
ps.setString(1, name);
ps.setString(2, surname);
ps.setString(3, company);
ps.setString(4, address);
ps.setString(5, addressTwo);
ps.executeUpdate();
System.out.println("Data Added");
} catch (Exception e) {
System.out.println("Error occured when adding value to database : " + e );
}
}

May I suggest you implement addCustomer like this. Use a local Statement and create it by using try-with-resource style and then set your parameters for the query
public void addCustomer(String name, String surname, String company, String adress, String adressTwo){
String addQuery = "insert into musteri (name,surname,company,adress,adressTwo) values (?,?,?,?,?)" ;
try (PreparedStatement stmt = con.prepareStatement(addQuery)) {
stmt.setString(1, name);
stmt.setString(2, surname);
stmt.setString(3, company);
stmt.setString(4, adress);
stmt.setString(5, adressTwo);
stmt.executeUpdate();
System.out.println("Data Added");
} catch (Exception e) {
System.out.println("Error occured when adding value to database : " + e );
}
}

Can getString() method of ResultSet can be used for getting the value of a TEXT type column from a MySQL table?

I am trying to retrieve the value of a TEXT field from a table in a MySQL database.
MySQL version is 5.6.21
& I am using mysql-connector-java-5.1.18-bin.jar
My file is given below
import java.sql.*;
public class DatabaseConnection {
static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
static final String DB_URL = "jdbc:mysql://localhost/book";
// database credentials
static final String USER = "username";
static final String PASS = "password";
public static void main(String[] args) {
Connection conn = null;
Statement stmt = null;
try {
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Connecting to database...");
conn = DriverManager.getConnection(DB_URL, USER, PASS);
System.out.println("Creating statement...");
stmt = conn.createStatement();
String query;
query = "Select b_name, description columns from brands";
ResultSet rs = stmt.executeQuery(query);
while(rs.next()) {
String first_name = rs.getString("b_name");
String description = rs.getString("description");
System.out.println(first_name);
System.out.println(description);
}
rs.close();
stmt.close();
conn.close();
} catch(SQLException se) {
se.printStackTrace();
} catch(ClassNotFoundException cnfe) {
cnfe.printStackTrace();
}
finally{
//finally block used to close resources
try{
if(stmt!=null)
stmt.close();
} catch(SQLException se2){
}// nothing we can do
try{
if(conn!=null)
conn.close();
} catch(SQLException se){
se.printStackTrace();
}//end finally try
}//end try
System.out.println("Goodbye!");
}
}
This says that my column does not exist although I have tried this on another table, it works on VARCHAR columns but not on TEXT columns
This error shows up:
But the table has a column named description:

The problem is NOT about the column type being text.
You can get the value of a TEXT type using getString.
You can verify in the documentation.
The problem is in the query:
query = "Select b_name, description columns from brands";
"columns" there is a mistake.
Written this way, the description column is in fact renamed to columns in your result set.
If you did rs.getString("columns") you would get the value.
But that's not what you want to do. You want to fix the query by dropping that word:
query = "Select b_name, description from brands";

how to update mysql with textfield and jcombobox in java

private void UpdateActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
//Update
try{
if(!(jTextField1.getText().isEmpty())){
Connection myConn= null;
Statement myStmt= null;
ResultSet myRs= null;
String user= "root";
String pass= "passwd14";
//Get Connection to database
myConn = DriverManager.getConnection("jdbc:mysql://localhost:3306/company",user, pass);
//Create a Statement
myStmt = myConn.createStatement();
//Prepared Statement
PreparedStatement pst=null;
try{
String on= jTextField1.getText();
//Prepare statement Execution
String sql2 = "UPDATE amazon SET name =?, mob =?, oddt =? FROM amazon WHERE odn ='"+on+"'";
pst=myConn.prepareStatement(sql2);
//pst.setString(4,jTextField1.getText());
pst.setString(1,jTextField2.getText());
pst.setString(2,jTextField6.getText());
pst.setString(3,jTextField5.getText());
pst.executeUpdate();
//Update ComboBox
String s= (String)jComboBox1.getSelectedItem();
jComboBox1.setSelectedItem(s);
String s2= (String)jComboBox2.getSelectedItem();
jComboBox1.setSelectedItem(s2);
JOptionPane.showMessageDialog(this,"Record Saved..");
}catch (Exception e){
JOptionPane.showMessageDialog(this,"Error");
}
}
}catch (Exception ex){
JOptionPane.showMessageDialog(this," This Error.. Keeps Showing up");
}
}
This is the database I want to update :
amazon(name, mob, iss, stat, oddt, odn)
that is (name, mobile, issue, status, order_details, orderno)

Update Query
It will work
String sql2 = "UPDATE amazon SET name =?, mob =?, oddt =? WHERE odn ='"+on+"'";

JButton is not enabling when have result set in Java

Following code is to enable button greceived_btnwhen result set contain data.
But the button is not enabling when the SQL criteria met.
What is the error here?
public void enableBtn() throws SQLException{
greceived_btn.setEnabled(false);
if(poNo.getSelectedItem()!=null){
String no = poNo.getSelectedItem().toString();
String not="no";
String sql = "SELECT * FROM pointoinvoce WHERE PONo=? AND GoodsRecieved=?";
pst=conn.prepareStatement(sql);
pst.setString(1, no);
pst.setString(2, not);
rs=pst.executeQuery();
if(rs.next()){
greceived_btn.setEnabled(true);
}else{
greceived_btn.setEnabled(false);
}
}
}

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