SQL expert require for WP custom post in PHP site

General information for the website: Leisure
Description of requirements/features: I am looking for someone to edit some existing (working) sql code from 2 tables in the WP database. The sql has been started but it needs editing. I will provide a sql file with the 2 tables in. I am using the 'Advanced custom fields' plugin.

Edits required:

1. Unique key creation
2. Addition of custom field values from post_meta table (credit, internal_link, internal_link_text, external_link, external_link_text
3. Filter by category

Will also take advice if existing sql is incorrect! Thanks
Extra notes: SELECT postid, title, post_name, date, content, credit, CONCAT(LEFT(image, LENGTH(image) - LOCATE('.', REVERSE(image))),'.',SUBSTRING_INDEX(image, '.', -1)) AS image FROM ( SELECT p.post_title AS title, p.post_status AS 'status', p.post_date AS date, p.post_content AS content, p.post_name AS post_name, m.meta_value AS credit, p.id AS postid, (SELECT `guid` FROM wp_posts WHERE id = m.meta_value) AS image FROM wp_posts p, wp_postmeta m WHERE p.post_type = 'post' AND p.post_status = 'publish' AND p.id = m.post_id AND m.meta_key = '_thumbnail_id' ORDER BY date DESC LIMIT 5) TT