如何将列的值赋给变量？

 conn = psycopg2.connect(database="your_database", user="your_username", password="your_password", host="your_host", port="your_port")

 cursor = conn.cursor()

 cursor.execute("SELECT column_name FROM table_name")

 column_value = cursor.fetchone()[0]

 conn.close()

 ```

 Connection conn = DriverManager.getConnection("jdbc:postgresql://your_host:your_port/your_database", "your_username", "your_password");

 Statement stmt = conn.createStatement();

 ResultSet rs = stmt.executeQuery("SELECT column_name FROM table_name");

 rs.next();

 String column_value = rs.getString("column_name");

 conn.close();

 ```

 const connection = mysql.createConnection({

   host: 'your_host',

   user: 'your_username',

   password: 'your_password',

   database: 'your_database'

 });

 connection.connect();

 connection.query('SELECT column_name FROM table_name', function (error, results, fields) {

   if (error) throw error;

   const column_value = results[0].column_name;

   connection.end();

 });

 ```