jdbc增删查改代码

以下是一个简单的JDBC增删查改的示例代码：

1. 建立数据库连接：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class DatabaseConnection {
    private static final String URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "password";

    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(URL, USERNAME, PASSWORD);
    }
}

2. 添加数据：

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class InsertData {
    public static void main(String[] args) {
        String sql = "INSERT INTO users (name, age) VALUES (?, ?)";
        try (Connection conn = DatabaseConnection.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setString(1, "John");
            stmt.setInt(2, 25);
            stmt.executeUpdate();
            System.out.println("Data inserted successfully.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

3. 删除数据：

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class DeleteData {
    public static void main(String[] args) {
        String sql = "DELETE FROM users WHERE id = ?";
        try (Connection conn = DatabaseConnection.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setInt(1, 1);
            stmt.executeUpdate();
            System.out.println("Data deleted successfully.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

4. 修改数据：

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;

public class UpdateData {
    public static void main(String[] args) {
        String sql = "UPDATE users SET age = ? WHERE id = ?";
        try (Connection conn = DatabaseConnection.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql)) {
            stmt.setInt(1, 30);
            stmt.setInt(2, 1);
            stmt.executeUpdate();
            System.out.println("Data updated successfully.");
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

5. 查询数据：

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class QueryData {
    public static void main(String[] args) {
        String sql = "SELECT * FROM users";
        try (Connection conn = DatabaseConnection.getConnection();
             PreparedStatement stmt = conn.prepareStatement(sql);
             ResultSet rs = stmt.executeQuery()) {
            while (rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                System.out.println("ID: " + id + ", Name: " + name + ", Age: " + age);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}