Wordpress - Delete tables from database when deleting plugin

You could do this using the WordPress uninstall.php support:

<?php
    if( ! defined( 'WP_UNINSTALL_PLUGIN' ) ) exit();
    global $wpdb;
    $wpdb->query( "DROP TABLE IF EXISTS NestoNovo" );
    delete_option("my_plugin_db_version");
?>

This uninstall.php file is called when your plugin is deleted.

Enter code here:

register_deactivation_hook( __FILE__, 'my_plugin_remove_database' );
function my_plugin_remove_database() {
     global $wpdb;
     $table_name = $wpdb->prefix . 'NestoNovo';
     $sql = "DROP TABLE IF EXISTS $table_name";
     $wpdb->query($sql);
     delete_option("my_plugin_db_version");
}   

You need to use register_uninstall_hook hook instead of register_deactivation_hook to delete tables from the database.

register_deactivation_hook fires when we deactivate a plugin and register_uninstall_hook fires when we want to remove/delete our plugin.

Please use this code if you have only one table:

function delete_plugin_database_table(){
    global $wpdb;
    $table_name = $wpdb->prefix . 'table_name';
    $sql = "DROP TABLE IF EXISTS $table_name";
    $wpdb->query($sql);
}

register_uninstall_hook(__FILE__, 'delete_plugin_database_table');

If you have more than two tables then you use this code:

function delete_plugin_database_tables(){
        global $wpdb;
        $tableArray = [   
          $wpdb->prefix . "table_name1",
          $wpdb->prefix . "table_name2",
          $wpdb->prefix . "table_name3",
          $wpdb->prefix . "table_name4",
       ];

      foreach ($tableArray as $tablename) {
         $wpdb->query("DROP TABLE IF EXISTS $tablename");
      }
    }

    register_uninstall_hook(__FILE__, 'delete_plugin_database_tables');

Reference Links:

https://developer.wordpress.org/reference/functions/register_uninstall_hook/ https://developer.wordpress.org/plugins/plugin-basics/uninstall-methods/