WordPress List Posts by First Title Letter

first-title-letter-query.php

<?php
global $wpdb;

$first_char = esc_attr($_GET[$search_key]);

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

if ( $postids ) {
	$args = array(
		'post__in' => $postids,
		'post_type' => 'product',
		'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 '<p>List of Posts Titles beginning with the letter <strong>'. $first_char . '<strong></p>';
		$counter = 1;
		while ($my_query->have_posts()) : $my_query->the_post(); ?>
		<p>
			<span><?php echo $counter++; ?></span>
			<a href="<?php the_permalink() ?>" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a>
		</p>
		<?php endwhile;
	}

	wp_reset_query();
}
?>

This code solve my life, Thank you very match!