How to Create a Table
In SQL, the CREATE TABLE statement is used to create a new table in a database. It defines the table name, columns, their data types, and (optionally) constraints such as PRIMARY KEY, FOREIGN KEY, DEFAULT values, and UNIQUE constraints.
Example: Creating a Table in Java
Properties on jtable
à tblFiels
Source Code:
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import java.sql.*;
import javax.swing.*;
import javax.swing.table.DefaultTableModel;
public class CreateTableForm extends javax.swing.JFrame {
/**
* Creates new form CreateTableForm
*/
Connection con;
public CreateTableForm() {
initComponents();
loadDatabases(); // load DBs into combo when form opens
// Setup JTable model
DefaultTableModel model = (DefaultTableModel) tblFields.getModel();
tblFields.setModel(model);
// Create JComboBox with allowed SQL data types
String[] dataTypes = {"INT", "VARCHAR(50)", "DATE", "DECIMAL(10,2)", "TEXT"};
JComboBox<String> comboBox = new JComboBox<>(dataTypes);
// Set the comboBox as editor for the second column (Data Type)
tblFields.getColumnModel().getColumn(1).setCellEditor(new DefaultCellEditor(comboBox));
}
private void loadDatabases() {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
// Connect to MySQL server (no specific DB yet)
con = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/?useSSL=false&serverTimezone=Asia/Phnom_Penh",
"root", // your MySQL username
"root" // your MySQL password
);
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery("SHOW DATABASES");
// Clear old items first
comboDatabases.removeAllItems();
while (rs.next()) {
comboDatabases.addItem(rs.getString(1)); // add DB name
}
rs.close();
stmt.close();
} catch (Exception e) {
JOptionPane.showMessageDialog(this, "Error: " + e.getMessage());
}
}
private void btnCreateTableActionPerformed(java.awt.event.ActionEvent evt) {
// Get selected database from combo box
String selectedDB = comboDatabases.getSelectedItem().toString();
String tableName = txtTableName.getText().trim();
if (tableName.isEmpty()) {
JOptionPane.showMessageDialog(this, "Please enter table name");
return;
}
// Validate table name (optional but recommended)
if (!tableName.matches("[a-zA-Z_][a-zA-Z0-9_]*")) {
JOptionPane.showMessageDialog(this, "Invalid table name. Use letters, numbers, and underscores only.");
return;
}
// Build SQL dynamically from JTable
DefaultTableModel model = (DefaultTableModel) tblFields.getModel();
StringBuilder sql = new StringBuilder("CREATE TABLE `" + tableName + "` (");
boolean firstFieldAdded = false;
for (int i = 0; i < model.getRowCount(); i++) {
String field = model.getValueAt(i, 0) != null ? model.getValueAt(i, 0).toString().trim() : "";
String type = model.getValueAt(i, 1) != null ? model.getValueAt(i, 1).toString().trim() : "";
if (!field.isEmpty() && !type.isEmpty()) {
if (firstFieldAdded) {
sql.append(", "); // comma between columns
}
sql.append("`").append(field).append("` ").append(type);
firstFieldAdded = true;
}
}
if (!firstFieldAdded) {
JOptionPane.showMessageDialog(this, "Please enter at least one field with a valid data type");
return;
}
sql.append(")"); // close parentheses
// Execute SQL
try {
Class.forName("com.mysql.cj.jdbc.Driver");
try (Connection con = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/" + selectedDB + "?useSSL=false&serverTimezone=Asia/Phnom_Penh",
"root", "root");
Statement stmt = con.createStatement()) {
stmt.executeUpdate(sql.toString());
JOptionPane.showMessageDialog(this, "Table '" + tableName + "' created successfully in database '" + selectedDB + "'!");
}
} catch (Exception e) {
e.printStackTrace();
JOptionPane.showMessageDialog(this, "Error: " + e.getMessage());
}
}
Result:
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