#1

CREATE TABLE avg_tests (val);

#2

INSERT INTO avg_tests (val)
VALUES
 (1),
 (2),
 (10.1),
 (20.5),
 ('8'),
 ('B'),
 (NULL),
 (x'0010'),
 (x'0011');

#3

SELECT rowid,
       val
  FROM avg_tests;

#4

SELECT
	avg(val)
FROM
	avg_tests
WHERE
	rowid < 5;

#5

SELECT
	avg(val)
FROM
	avg_tests;

#6

INSERT INTO avg_tests (val)
VALUES (10.1);

#7

SELECT
	avg(val)
FROM
	avg_tests;

#8

SELECT
	avg(DISTINCT val)
FROM
	avg_tests;

#9

SELECT
	avg(milliseconds)
FROM
	tracks;

#10

SELECT
	albumid,
	avg(milliseconds)
FROM
	tracks
GROUP BY
	albumid;

#11

SELECT
	tracks.albumid,
	title,
	round(avg(milliseconds), 2) avg_length
FROM
	tracks
INNER JOIN albums ON albums.AlbumId = tracks.albumid
GROUP BY
	tracks.albumid;

#12

SELECT
	tracks.albumid,
	title,
	round(avg(milliseconds),2)  avg_leng
FROM
	tracks
INNER JOIN albums ON albums.AlbumId = tracks.albumid
GROUP BY
	tracks.albumid
HAVING
	avg_leng BETWEEN 100000 AND 200000;