Trying to check if a condition is true, skip the function

Thanks.
It worked.
However it turns out that its not returning what I need.

How do I check if there is a “featured image” attached to a post?

I’ve tried

global $post; global $wpdb;
	$attached_file_check = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_parent = '$post->ID' AND post_status = 'inherit' AND post_type='attachment' ORDER BY post_date DESC LIMIT 1");

if( get_post_meta($post->ID, "_videoembed", true) && !isset($attached_file_check) )
	{
//function to attach existing videothumbnail goes here
}

It keeps firing the function leading to thousands of entries in my database to same thumbnails.

I am going to paste the entire function below, just in case you see other errors in my code.

function postmeta_img_fromvideo() {
	global $post; global $wpdb;
	$attached_file_check = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_parent = '$post->ID' AND post_status = 'inherit' AND post_type='attachment' ORDER BY post_date DESC LIMIT 1");
//if(get_post_meta($post->ID, "_videoembed", true) AND get_post_meta($post->ID, "_thumbnail_id", true) != true)
if( get_post_meta($post->ID, "_videoembed", true) && !isset($attached_file_check) )
	{
		$videofilename = get_post_meta($post->ID, "_videoembed", true);
		$vid_sub_ext = substr($videofilename, 0 , -4);

		$thumb = $vid_sub_ext . '_1.jpg';
		$thumbnail = str_replace('http://www.mydomainname.com/wp-content/', '', $thumb);

		$wp_filetype = wp_check_filetype(basename($thumbnail), null );
		$attachment = array(
	     'post_mime_type' => $wp_filetype['type'],
	     'post_title' => get_the_title(),
	     'post_content' => 'Image for '.get_the_title(),
	     'post_status' => 'inherit'
		);

		wp_insert_attachment($attachment, $thumbnail, $post->ID);

		// Get Attachment ID for Post
		$attachment_id = $wpdb->get_var("SELECT ID FROM $wpdb->posts WHERE post_parent = '$post->ID' AND post_status = 'inherit' AND post_type='attachment' ORDER BY post_date DESC LIMIT 1");

		// Attached Image as Featured Thumbnail in Post
		update_post_meta($post->ID, "_thumbnail_id", $attachment_id);

	}
}
add_action('the_post','postmeta_img_fromvideo');

Thanks again for your help. I’m trying to automate this stuff as much as possible.

I’m using the following function at the top of my functions.php

add_theme_support( ‘post-thumbnails’ );

I believe this activates the featured thumbnails and that its supposed to be supported by the new WP 3.0 (Oh, I’m using 3.0.1)