### Database Schema:
CREATE TABLE podcasts (
	podcast_id	TEXT	NULL	PRIMARY KEY,
	itunes_id	INTEGER	NOT NULL,
	slug	TEXT	NOT NULL,
	itunes_url	TEXT	NOT NULL,
	title	TEXT	NOT NULL
);

CREATE TABLE reviews (
	podcast_id	TEXT	NOT NULL,
	title	TEXT	NOT NULL,
	content	TEXT	NOT NULL,
	rating	INTEGER	NOT NULL,
	author_id	TEXT	NOT NULL,
	created_at	TEXT	NOT NULL,
	foreign key (podcast_id) references podcasts (podcast_id)
);

CREATE TABLE runs (
	run_at	TEXT	NOT NULL,
	max_rowid	INTEGER	NOT NULL,
	reviews_added	INTEGER	NOT NULL
);

CREATE TABLE categories (
	podcast_id	TEXT	NOT NULL	PRIMARY KEY,
	category	TEXT	NOT NULL	PRIMARY KEY,
	foreign key (podcast_id) references podcasts (podcast_id)
);

### User's Query:
Of the arts-books and arts-design categories, which one has more podcasts and what is the numerical difference between them?

### Extra Knowledge:
arts-books' and 'arts-design' are category; numerical difference = Subtract(Count(podcast_id(category = 'arts-books')), Count(podcast_id(category = 'arts-design'))); one has much more podcast refers to Max(Count(podcast_id))
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"