Querying Wordpress thumbnails

I am trying to get the thumbnail meta data for the posts in my wordpress blog together with their category and some other data. The thumbnail data is serialized and I will unserialize it later.

Here is the query I have:

    SELECT wpostmeta.meta_value AS url,
    wposts.post_content, wposts.post_title, wposts.post_status, wposts.post_name,
    cat_terms.name AS category_name, cat_terms.term_id AS category_id,
    ttable.meta_value AS thumb_data
    FROM `wp_postmeta` AS wpostmeta,
    `wp_posts` AS wposts
    INNER JOIN wp_term_relationships AS cat_term_relationships ON (wposts.ID = cat_term_relationships.object_id)
    INNER JOIN wp_term_taxonomy AS cat_term_taxonomy ON (cat_term_relationships.term_taxonomy_id = cat_term_taxonomy.term_taxonomy_id AND cat_term_taxonomy.taxonomy = 'category')
    INNER JOIN wp_terms AS cat_terms ON (cat_term_taxonomy.term_id = cat_terms.term_id)
    LEFT JOIN `wp_postmeta` AS ttable ON (wposts.ID = ttable.post_id AND ttable.meta_key = '_wp_attachment_metadata')
    WHERE wpos开发者_Python百科ts.ID = wpostmeta.post_id AND wpostmeta.meta_key = 'url'
    AND wposts.post_type = 'post'

Everything works except for the attachment part. 'thumb_data' is NULL.

Could you please help me fix this?

This query solved my problem:

$sql = "SELECT wposts.ID AS ID, thumbposts.ID AS thumbposts_ID,
        postmeta.meta_value AS url,
        wposts.post_content, wposts.post_title, wposts.post_status, wposts.post_name,
        cat_terms.name AS category_name, cat_terms.term_id AS category_id,
        thumb.meta_value AS thumb_data

        FROM `wp_postmeta` AS postmeta,
        `wp_posts` AS thumbposts,
        `wp_postmeta` AS thumb,
        `wp_posts` AS wposts

        INNER JOIN wp_term_relationships AS cat_term_relationships ON (wposts.ID = cat_term_relationships.object_id)
        INNER JOIN wp_term_taxonomy AS cat_term_taxonomy ON (cat_term_relationships.term_taxonomy_id = cat_term_taxonomy.term_taxonomy_id AND cat_term_taxonomy.taxonomy = 'category')
        INNER JOIN wp_terms AS cat_terms ON (cat_term_taxonomy.term_id = cat_terms.term_id)

        WHERE wposts.ID = postmeta.post_id
        AND postmeta.meta_key = 'url'

        AND thumbposts.post_parent = wposts.ID
        AND thumbposts.post_type = 'attachment'

        AND thumb.post_id = thumbposts.ID
        AND thumb.meta_key = '_wp_attachment_metadata'

        AND wposts.post_type = 'post'";

    if($filter == 1){
        $sql .= " AND cat_terms.term_id = '1'";
    }
    if($filter == 2){
        $sql .= " AND cat_terms.term_id = '3'";
    }

    $sql .= " GROUP BY wposts.ID
        ORDER BY wposts.post_date ASC";

Can you explain exactly what you are trying to achieve - there is no real need to go direct to the database in the vast number of situations.

For example you can use get_posts with 'post_type'=>'attachment' and 'post_mime_type'=>'image' to get image attachments and then output the metadata, and there are many functions inbuilt to deal with resizing, displaying and cropping the thumbnails, such as get_post_thumbnail() etc.