### 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:
What is the average rating of all the podcasts with reviews created in 2019?

### Extra Knowledge:
created in 2019 refers to created_at BETWEEN '2019-01-01T00:00:00' and '2019-12-31T23:59:59'; average rating  = Divide (Sum(rating), Count(podcast_id))
SELECT AVG(rating) FROM reviews WHERE created_at BETWEEN '2019-01-01T00:00:00-07:00' AND '2019-12-31T23:59:59-07:00'