UPDATE mangas
SET chapter_flags = 0
WHERE chapter_flags = -1;
UPDATE mangas
SET viewer = 0
WHERE viewer = -1;
UPDATE mangas
SET date_added = 0
WHERE date_added = -1;
UPDATE mangas
SET cover_last_modified = 0
WHERE cover_last_modified = -1;
UPDATE mangas
SET last_update = 0
WHERE last_update = -1;
UPDATE categories
SET manga_order = "";