MySQL INSERT IF NOT EXIST else DELETE row
INSERT INTO wp_postmeta (post_id, meta_key) SELECT ?id, ‘page_title’
FROM DUAL WHERE NOT EXISTS (
    SELECT meta_id FROM wp_postmeta WHERE post_id = ?id AND meta_key = ‘page_title’);
UPDATE wp_postmeta SET meta_value = ?page_title WHERE post_id = ?id AND meta_key = ‘page_title’;