-- Database schema
| runs : run_at [ TEXT ] , max_rowid [ INTEGER ] , reviews_added [ INTEGER ] | podcasts : podcast_id [ TEXT ] primary_key , itunes_id [ INTEGER ] , slug [ TEXT ] , itunes_url [ TEXT ] , title [ TEXT ] | reviews : podcast_id [ TEXT ] , title [ TEXT ] , content [ TEXT ] , rating [ INTEGER ] , author_id [ TEXT ] , created_at [ TEXT ] | categories : podcast_id [ TEXT ] , category [ TEXT ] |
-- -- Of the arts-books and arts-design categories, which one has more podcasts and what is the numerical difference between them?

SELECT ( SELECT category FROM categories WHERE category = 'arts-books' OR category = 'arts-design' GROUP BY category ORDER BY COUNT(podcast_id) DESC LIMIT 1 ) "has more podcasts" , ( SELECT SUM(CASE WHEN category = 'arts-books' THEN 1 ELSE 0 END) - SUM(CASE WHEN category = 'arts-design' THEN 1 ELSE 0 END) FROM categories ) "differenct BETWEEN arts-books and arts-design";