Order Posts by Alphabetical for Each Letter

This is what I find for this question. Two codes I found were coded by MichaelH from wordpress.org. Even he won’t probably see this post, I want to thank him.

Now, I just need to sort these posts from specified one category. If anyone knows how to sort them with specified category, please help me. Thanks.

   <?php
    //get all post IDs for posts beginning with cap B, in title order,
    //display posts
    $first_char="B";

    $postids=$wpdb->get_col($wpdb->prepare("
    SELECT      ID
    FROM        $wpdb->posts
    WHERE       SUBSTR($wpdb->posts.post_title,1,1) = %s
    ORDER BY    $wpdb->posts.post_title",$first_char)); 

    if ($postids) {
    $args=array(
      'post__in' => $postids,
      'post_type' => 'post',
      'post_status' => 'publish',
      'posts_per_page' => -1,
      'caller_get_posts'=> 1
    );
    $my_query = null;
    $my_query = new WP_Query($args);
    if( $my_query->have_posts() ) {
     echo 'List of Posts Titles beginning with the letter '. $first_char;
      while ($my_query->have_posts()) : $my_query->the_post(); ?>
        <p><a href="https://wordpress.stackexchange.com/questions/147933/<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></p>
        <?php
      endwhile;
    }
    wp_reset_query();  // Restore global post data stomped by the_post().
    }
    ?>