Develop Reference

cannot set null to a unique column

so this is my table
CREATE TABLE "client" (
"id" INTEGER,
"name" TEXT COLLATE NOCASE,
"surname" TEXT COLLATE NOCASE,
"number" TEXT UNIQUE COLLATE NOCASE,
"car_brand" TEXT,
"modele" TEXT,
"phone_nbr" TEXT,
PRIMARY KEY("id" AUTOINCREMENT));
when im adding a new statment from my java application i can add only one time NULL to the column number but i can add many nulls from the db browser
this is the code that i use
String number = tf_number.getText();
if(tf_number.getText().trim().isEmpty())
number = null;
String name = tf_name.getText();
String surname = tf_surname.getText();
String phoneNbr = tf_phoneNbr.getText();
String car_brand = tf_brand.getText();
String modele = tf_modele.getText();
Client c = new Client(name, surname, number, car_brand, modele, phoneNbr);
ClientCRUD pcd = new ClientCRUD();
pcd.addClient(p);
and this is the sql error
[SQLITE_CONSTRAINT_UNIQUE] A UNIQUE constraint failed (UNIQUE constraint failed: client.number)
this is the addClient() fonction
public void addClient(Client t) {
try {
String requete = "INSERT INTO CLIENT(name,surname,number,car_brand,MODELE,phone_nbr)"
+ "VALUES ('"+t.getClientName()+"','"+t.getClientSurname()+"','"+t.getNumber()+"',"
+ "'"+t.getCarBrand()+"','"+t.getModele()+"','"+t.getPhone()+"')";
Statement st = MyConnection.getInstance().getCnx()
.createStatement();
st.executeUpdate(requete);
System.out.println("Client added");
} catch (SQLException ex) {
System.out.println(ex.getMessage());
}
}
any solution ?

public void save(Person person) {
String query = "INSERT INTO person_info (" +
" name_p, " +
" age, " +
" address, " +
" email " +
")" +
"VALUES(?, ?, ?, ?)";
try(Connection connection = dbConnection.getConnection()) {
PreparedStatement prepStatement = connection.prepareStatement(query);
prepStatement.setString(1, person.getName());
prepStatement.setInt(2, person.getAge());
prepStatement.setString(3, person.getAddress());
prepStatement.setString(4, null);
prepStatement.execute();
}
catch (SQLException e){
e.printStackTrace();
}
}
##This will solve your problem

You code inserts the string "null" and not a real null like your browser do.
So there can be only 1 string with value "null" in that unique column.
You can use preparedStatement with parameters instead of the statement you use.
E.g:
PreparedStatement preparedStatement = connection.prepareStatement(sql))
This answers how to insert null using prepared statement: Insert null using prepared statement
And your sql string for the query should have the parameters.
See more about prepared statements: Prepared Statements Tutorial

how to insert into mysql database with java

i want to insert inputs i take from user into mysql database the connection is right but the insertion gives me error
com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: 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 ''u_fname',
'u_lname', 'u_uname', 'u_pass', 'u_age', 'u_adderess') values('20','o'
at line 1
My code is:
public void adduser(User s) {
try {
sql = "insert into users ('u_fname', 'u_lname', 'u_uname', 'u_pass', 'u_age', 'u_adderess')"
+ "values('" + s.getFirstname() + "','" + s.getLastname()
+ "','" + s.getUsername() + "','" + s.getPassword() + "','" + s.getAge() + "','" + s.getAdderss() + "')";
stmt = conn.createStatement();
int i = stmt.executeUpdate(sql);
if (i > 0) {
System.out.println("ROW INSERTED");
} else {
System.out.println("ROW NOT INSERTED");
}
} catch (Exception e) {
System.out.println(e);
}
}

To insert into mysql, follow these steps-
Create a Java Connection to our example MySQL database. I believe you already took care of it. It will be something like this-
String myDriver = "org.gjt.mm.mysql.Driver";
String myUrl = "jdbc:mysql://localhost/test";
Class.forName(myDriver);
Connection conn = DriverManager.getConnection(myUrl, "root", "");
Create a SQL INSERT statement, using the Java PreparedStatement
syntax. Your PreparedStatement SQL statement will be as following this format-
String sql = " insert into users (first_name, last_name, date_created, is_admin, num_points)"
+ " values (?, ?, ?, ?, ?)";
Set the fields on our Java PreparedStatement object. It will done as-
PreparedStatement preparedStmt = conn.prepareStatement(sql);
preparedStmt.setString (1, s.first_name);
preparedStmt.setString (2, s.last_name);
preparedStmt.setDate (3, s.date_created);
preparedStmt.setBoolean(4, s.is_admin);
preparedStmt.setInt (5, s.num_points);
Execute a Java PreparedStatement.
preparedStmt.execute();
Close our Java MYSQL database connection.
conn.close();
Catch any SQL exceptions that may come up during the process.
catch (Exception e)
{
System.err.println("Got an exception!");
// printStackTrace method
// prints line numbers + call stack
e.printStackTrace();
// Prints what exception has been thrown
System.out.println(e);
}

Java updating mysql row if id already exists

I have a simple form with 5 fields. (txtID, txtFirstName, txtLastName, txtCheque, txtSavings). All I want to do is inserting these fields into my database table "accounts". Before that step I want to check if the ID from my txtID field already exists in my database. If yes then I want to update the database row with the content from the fields. And if not I want to create a new row with the content. So far the check if the ID exists in my DB works but if click on my btn I get the following error message: I dont relly know what I'm doing wrong.
com.mysql.jdbc.exceptions.MySQLSyntaxErrorException: 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 '(LastName,
FirstName,Cheque,Savings) VALUES('Tester','Markus','450.00','50.00" at
line 1
private void btnUpdateActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
try{
String id = txtID.getText();
String checkid ="SELECT * FROM accounts where ID=?";
pst=conn.prepareStatement(checkid);
pst.setString(1, id);
rs = pst.executeQuery();
boolean recordAdded = false;
while(!rs.next()){
recordAdded = true;
}
if(recordAdded){
// the statement for inserting goes here.
}else{
String sql ="UPDATE accounts SET " + "(LastName,FirstName,Cheque,Savings) VALUES" + "(?,?,?,?)";
pst=conn.prepareStatement(sql);
pst.setString(1,txtLastName.getText());
pst.setString(2,txtFirstName.getText());
pst.setString(3,txtCheque.getText());
pst.setString(4,txtSavings.getText());
pst.executeUpdate();
getAllAccounts();
JOptionPane.showMessageDialog(null, "Customer Updated");
}
}
catch(Exception e){
JOptionPane.showMessageDialog(null, e);
}
finally {
try{
rs.close();
pst.close();
getAllAccounts();
}
catch(Exception e) {
}
}
}

do you let me to make some changes in your code?
private void btnUpdateActionPerformed(java.awt.event.ActionEvent evt) {
try {
String sql = "UPDATE accounts SET LastName = ?, FirstName = ?, Cheque = ?, Savings = ? where id = ?";
pst=conn.prepareStatement(sql);
pst.setString(1,txtLastName.getText());
pst.setString(2,txtFirstName.getText());
pst.setString(3,txtCheque.getText());
pst.setString(4,txtSavings.getText());
pst.setString(5,txtID.getText());
int updatedRowCount = pst.executeUpdate();
// no record with id = txtID
if(updatedRowCount == 0) {
pst.close();
sql = "insert into accounts (ID,LastName,FirstName,Cheque,Savings) values (?,?,?,?,?,?) ";
pst = conn.prepareStatement(sql);
pst.setString(1,txtID.getText());
pst.setString(2,txtLastName.getText());
pst.setString(3,txtFirstName.getText());
pst.setString(4,txtCheque.getText());
pst.setString(5,txtSavings.getText());
pst.executeUpdate();
}
getAllAccounts();
JOptionPane.showMessageDialog(null, updatedRowCount > 0 ? "Customer Updated" : "Customer Inserted");
}
catch(Exception e){
getAllAccounts();
JOptionPane.showMessageDialog(null, e);
}
finally {
try{
pst.close();
}
catch(Exception e) {
}
}
}

SQL in Prepared Statement throwing SQL exception

I'm trying to figure out why this code is throwing an SQL exception. When I run this code it prints "Bad SQL in customer insert ps", which is the message in that inner catch block. I've got multiple prepared statements with SQL inserts like this both in this class and also elsewhere in my application. They're all working fine. I've looked through this one over and over again, and I can't figure out why this one is throwing an exception.
try {
Connection conn = DBconnection.getConnection();
PreparedStatement ps = conn.prepareStatement("SELECT customerId FROM customer WHERE customerName=\"" + name + "\";");
System.out.println(ps.toString());
ResultSet rs = ps.executeQuery();
if (rs.next()) {
customerId = rs.getString("customerId");
}
try {
PreparedStatement customerInsert = DBconnection.getConnection().prepareStatement("INSERT "
+ "INTO customer (customerName, addressId, active, createDate, createdBy, lastUpdate, lastUpdateBy)"
+ "VALUES(\"" + name + "\", " + addressId + ", " + active + ", UTC_TIMESTAMP(), \"" + LogInController.getUserName() + "\", UTC_TIMESTAMP(), \"" + LogInController.getUserName() + "\");");
customerInsert.executeUpdate();
System.out.println(customerInsert.toString());
System.out.println(rs.toString());
} catch (SQLException sq) {
System.out.println("Bad SQL in customer insert ps");
}
} catch (SQLException customerIdException) {
System.out.println("Bad SQL in customer ps");
}

You're using PreparedStatement as though you were using Statement. Don't put the parameters in the SQL, put in placeholder ? marks. Then use the various setXyz methods (setString, setInt, etc.) to fill in the parameters:
PreparedStatement customerInsert = DBconnection.getConnection().prepareStatement(
"INSERT INTO customer (customerName, addressId, active, createDate, createdBy, lastUpdate, lastUpdateBy)" +
"VALUES(?, ?, ?, ?, ?, ?, ?);"
);
customerInsert.setString(1, name);
customerInsert.setInt(2, addressId);
// ...etc. Notice that the parameter indexes start with 1 rather than 0 as you might expect

column not allowed here oracle with getText

I tried to save / edit / delete a new row in the database. writing in the gui values to be saved with getText ()
here is the code
Connection conn = Connessione.ConnecrDb();
Statement stmt = null;
ResultSet emps = null;
try{
String sql;
sql = "INSERT INTO PROGETTO.LIBRO (ISBN, DISPONIBILITA, TITOLO, CASA_EDITRICE, CODICE_AUTORE, GENERE, PREZZO)"
+ "VALUES (txt_isbn, txt_disp, txt_titolo, txt_casa, txt_autore, txt_genere, txt_prezzo)";
stmt = conn.createStatement();
emps = stmt.executeQuery(sql);
String ISBN= txt_isbn.getText();
String DISPONIBILITA= txt_disp.getText();
String TITOLO= txt_titolo.getText();
String CASA_EDITRICE= txt_casa.getText();
String CODICE_AUTORE= txt_autore.getText();
String GENERE= txt_genere.getText();
String PREZZO = txt_prezzo.getText();
JOptionPane.showMessageDialog(null, "SALVATO");
}catch(SQLException | HeadlessException e)
{
JOptionPane.showMessageDialog(null, e);
}
finally
{
try{
if (emps != null)
emps.close();
}
catch (SQLException e) { }
try
{
if (stmt != null)
stmt.close();
}
catch (SQLException e) { }
}
Getting this error: column not allowed here
Above code just takes care of insert operation. How can I delete and modify table record?

You have asked 2 different questions here
1. Column not allowed here
This happened because you have not passed values for any of parameter into insert statement.
I am not sure about your requirement however I will use PreparedStatement for this scenario.
Example
String insertTableSQL = "INSERT INTO DBUSER"
+ "(USER_ID, USERNAME, CREATED_BY, CREATED_DATE) VALUES"
+ "(?,?,?,?)";
PreparedStatement preparedStatement = dbConnection.prepareStatement(insertTableSQL);
preparedStatement.setInt(1, 11);
preparedStatement.setString(2, "MindPeace");
preparedStatement.setString(3, "system");
preparedStatement.setTimestamp(4, getCurrentTimeStamp());
preparedStatement .executeUpdate();
2. This code is only to save the data, delete, and modify an entire row how can I do?
Answer is very simple. You have to write code for the same :)
You need 3 SQL statement which has DELETE and UPDATE operation just like insert in above example.

String sql = "INSERT INTO PROGETTO.LIBRO (ISBN, DISPONIBILITA, TITOLO, "
+ "CASA_EDITRICE, CODICE_AUTORE, GENERE, PREZZO)"
+ "VALUES (?, ?, ?, ?, ?, ?, ?)";
try (PreparedStatement stmt = conn.createStatement()) {
NumberFormat numberFormat = NumberFormat.getInstance(Locale.ITALY);
String ISBN = txt_isbn.getText();
String DISPONIBILITA = txt_disp.getText();
String TITOLO = txt_titolo.getText();
String CASA_EDITRICE = txt_casa.getText();
String CODICE_AUTORE = txt_autore.getText();
String GENERE = txt_genere.getText();
BigDecimal PREZZO = new BigDecimal(
numberFormat.parse(txt_prezzo.getText()).doubleValue())
.setScale(2);
stmt.setString(1, ISBN);
stmt.setString(2, DISPONIBILITA);
stmt.setString(3, TITOLO);
stmt.setString(4, CASA_EDITRICE);
stmt.setString(5, CODICE_AUTORE);
stmt.setString(6, GENERE);
stmt.setBigDecimal(7, PREZZO);
int updateCount = stmt.executeUpdate();
JOptionPane.showMessageDialog(null, "SALVATO");
} catch(SQLException | HeadlessException e) {
JOptionPane.showMessageDialog(null, e);
}
Try-with-resources closes the stmt automatically.
The prepared statement replaces the value in the SQL with something like:
INSERT INTO table(column1, colum2, ....)
VALUES('De\'l Rey',
1234.50,
...)
for:
"De'l Rey"
1.234,50
updateCount should be 1 on success.

Wooow..true!!
I created three buttons to delete / update / insert and now it all works and automatically updates the tables.
you've been very very great. Thank you very much.
one last thing.
if I wanted to insert an error message when I delete / update etc "book not found" I tried to create an if:
Boolean found = false;
try{
sql= delete......
etc
if (!found)
JOptionPane.showMessageDialog(null, "NOT FOUND","ERRORE",JOptionPane.WARNING_MESSAGE);
etc...
Connection conn = Connessione.ConnecrDb();
Statement stmt = null;
ResultSet emps = null;
try{
String sql= "DELETE FROM progetto.libro WHERE isbn =?"; /
pst=(OraclePreparedStatement) conn.prepareStatement(sql);
pst.setString (1, txt_isbn.getText());
pst.execute();
JOptionPane.showMessageDialog(null, "ELIMINATO");
Update_table();
txt_isbn.setText("");
txt_disp.setText("");
txt_titolo.setText("");
txt_casa.setText("");
txt_autore.setText("");
txt_genere.setText("");
txt_prezzo.setText("");
}
catch (Exception e)
{
JOptionPane.showMessageDialog(null,e);
}
if you find the book must exit the book removed, or "not found". but as I deployed I always come out "deleted". why?
thanks again