How to auto Increment a primarykey in JDBC sql - sql

Question

can you please guys help me, i'm having trouble on making my primary key into auto-increment, My table name is books and the column that i want to be auto-increment is serial_no which is a primary key.
public class donate extends javax.swing.JFrame {
Connection con;
Statement stmt;
ResultSet rs;
PreparedStatement pst;
DefaultTableModel loginModel = new DefaultTableModel();
int curRow = 0;
/**
* Creates new form donate
*/
public donate() {
initComponents();
DoConnect();
showAll();
}
void showAll(){
try{
rs = stmt.executeQuery("SELECT * FROM books");
while(rs.next())
{
String book = rs.getString("book_title");
String categorie = rs.getString("category");
String status = rs.getString("book_status");
String donators = rs.getString("donator");
int serial_nos = rs.getInt("serial_no");
loginModel.addRow(new Object[]{book, categorie, status, donators, serial_nos});
}
}catch(SQLException err){
System.out.println(err);
}
}
void DoConnect( ) {
try{
//CONNECT TO THE DATABASE
String host = "jdbc:derby://localhost:1527/Dafuq7";
String uName ="Dafuq7";
String uPass ="Dafuq7";
con = DriverManager.getConnection(host, uName, uPass);
//EXECUTE SOME SQL AND LOAD THE RECORDS INTO THE RESULTSET
stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
ResultSet.CONCUR_UPDATABLE);
String sql = "SELECT * FROM books";
rs = stmt.executeQuery(sql);
}
catch(SQLException err){
JOptionPane.showMessageDialog(donate.this, err.getMessage());
}
}
and here is for may button, which when i input all the data will be submitted to my table books
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
String bookttl = bookt.getText();
String yourn = yn.getText();
String categ = cat.getSelectedItem().toString();
String bstat = bs.getSelectedItem().toString();
try {
rs.moveToInsertRow();
rs.updateString( "book_title", bookttl );
rs.updateString( "category", yourn );
rs.updateString( "book_status", categ );
rs.updateString( "donator", bstat );
loginModel.addRow(new Object[]{bookttl, yourn, categ, bstat});
rs.insertRow( );
stmt.close();
rs.close();
stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
String sql = "SELECT * FROM books";
rs = stmt.executeQuery(sql);
}
catch (SQLException err) {
System.out.println(err.getMessage() );
}// TODO add your handling code here:
}
BTW i found another way around by doing this, grabbing my table and reconstructing it and put this code in the create table script
SERIAL_NO INTEGER default AUTOINCREMENT: start 1 increment 1 not null primary key

Answer 1

Simply define your serial_no column as int primary key generated always as identity and then Derby will automatically assign the numbers for you. Here is some example code:
public static void main(String[] args) {
try (Connection conn = DriverManager.getConnection(
"jdbc:derby:C:/__tmp/derbytest;create=true")) {
String sql;
sql = "DROP TABLE books";
try (Statement s = conn.createStatement()) {
s.executeUpdate(sql);
} catch (Exception e) {
// assume table did not previously exist
}
sql = "CREATE TABLE books (" +
"serial_no int primary key " +
"generated always as identity, " +
"title varchar(100))";
try (Statement s = conn.createStatement()) {
s.executeUpdate(sql);
}
sql = "INSERT INTO books (title) VALUES (?)";
try (PreparedStatement ps = conn.prepareStatement(sql)) {
ps.setString(1, "The Book of Foo");
ps.executeUpdate();
ps.setString(1, "The Book of Bar");
ps.executeUpdate();
ps.setString(1, "The Book of Baz");
ps.executeUpdate();
}
sql = "SELECT * FROM books";
try (Statement s = conn.createStatement()) {
try (ResultSet rs = s.executeQuery(sql)) {
while (rs.next()) {
System.out.println(String.format(
"%d: %s",
rs.getInt("serial_no"),
rs.getString("title")));
}
}
}
} catch (SQLException se) {
se.printStackTrace(System.out);
System.exit(0);
}
}
which produces
1: The Book of Foo
2: The Book of Bar
3: The Book of Baz