How to run query and num_rows in wordpress

How to run query and num_rows in wordpress

      $query = $wpdb->get_results("SELECT wplc_postmeta.meta_id FROM wplc_postmeta WHERE 1 AND wplc_postmeta.meta_key = 'product_id' AND wplc_postmeta.meta_value = '$product_id'");
  $total_result_rows = $wpdb->num_rows;

  if($total_result_rows == 0)
       {
              //your code here
}


you can also use . $wpdb->prefix . if you dont know the table prefix
example-

function get_all_companies_selling( $product_id ){
    global $wpdb;
    $sql = "select post_id from " . $wpdb->prefix . "postmeta where
        meta_key = 'prefix_products' &&
        meta_value like '%%%s%%'";

    $product_id = 's:' . strlen( $product_id ) . ':"' . (int) $product_id . '";';
    $sql = $wpdb->prepare( $sql, $product_id );
    $res = $wpdb->get_results( $sql );

    return $res;
}

get_all_companies_selling( 331  );




 $args = array(
        'post_type'   => 'product',
        'post_status' => 'publish',
        'meta_key' => 'catagory',
        'showposts'  => 5,
        'orderby'     => 'rand',
        'meta_value' => $parent_post_id
        );
    $posts = get_posts( $args );

    // DO NOTHING
    if( !$posts )
        return;

    foreach( $posts as $post )
    {
       $catagroy_title = $product_details['catagory'];
       $meta = get_post_meta( $post->ID );
     $product_meta_details="";
     foreach ($meta as $key => $metavalue) {
      $product_meta_details[$key] = $metavalue[0];
     }
    
        $product_title = $post->post_title;


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Get related post or products based on meta key and values through wordpress function