My solution for the SQL Murder Mystery. Solve it for yourself at https://mystery.knightlab.com/

sql-murder-mystery.sql

WITH murder AS (
  -- determine details of the murder
  SELECT *
  FROM crime_scene_report
  WHERE date = 20180115
    AND TYPE = 'murder'
    AND city = 'SQL City'
),
first_witness AS (
  -- last house on Northwestern Dr belongs to Morty Schapiro
  SELECT *
  FROM person
  WHERE address_street_name = 'Northwestern Dr'
    AND address_number = (
      SELECT
        MAX(address_number)
      FROM
        person)
),
second_witness AS (
  -- name similar to "Annabel" and on Franklin Ave is Annabel Miller
  SELECT *
  FROM person
  WHERE name LIKE "%Annabel%"
    AND address_street_name = 'Franklin Ave'
),
witnesses AS (
  -- combine first_witness and second_witness
  SELECT person.*
  FROM person, first_witness, second_witness
  WHERE person.id = first_witness.id
    OR person.id = second_witness.id
),
witnesses_interview AS (
  -- what did they say? details:
  -- from witness 1
  -- - member of Get Fit Now
  -- - membership number of bag starts with 48Z and gold member
  -- - plate number like %H42W%
  -- from witness 2
  -- - worked out on 9 Jan
  SELECT *
  FROM interview
    JOIN witnesses ON interview.person_id = witnesses.id
),
with_48z AS (
  -- from witness 1's report
  SELECT *
  FROM get_fit_now_member
  WHERE id LIKE '48Z%'
    AND membership_status = 'gold'
),
checked_in_at_20180109 AS (
  -- from witness 2's report
  SELECT *
  FROM get_fit_now_check_in
  WHERE check_in_date = 20180109
),
suspect_bataks AS (
  -- from witness 1 and 2's reports
  SELECT *
  FROM person
    JOIN with_48z ON person.id = with_48z.person_id
    JOIN checked_in_at_20180109 ON with_48z.id = checked_in_at_20180109.membership_id
),
suspect_drivers AS (
  -- from witness 2's report
  SELECT *
  FROM person
    JOIN drivers_license ON person.license_id = drivers_license.id
      AND drivers_license.plate_number LIKE '%H42W%'
),
suspect AS (
  -- combining suspect_bataks and suspect_drivers leads us to one dude
  SELECT *
  FROM person
    JOIN suspect_bataks ON person.id = suspect_bataks.id
    JOIN suspect_drivers ON person.id = suspect_drivers.id
),
suspect_interview AS (
  -- now the plot thickens...
  -- I was hired by a woman with a lot of money.
  -- ... she's around 5'5" (65") or 5'7" (67").
  -- She has red hair and she drives a Tesla Model S.
  -- I know that she attended the SQL Symphony Concert 3 times in December 2017.
  SELECT interview.*, person.*
  FROM interview
    JOIN suspect ON interview.person_id = suspect.id
    JOIN person ON interview.person_id = person.id
),
employer_driver AS (
  -- from suspect's description: red hair, Tesla Model S, bet. 65 and 67
  SELECT *
  FROM drivers_license
  WHERE hair_color = 'red'
    AND car_make = 'Tesla'
    AND car_model = 'Model S'
    AND height >= 65
    AND height <= 67
),
employer_symphony AS (
  -- what are these people thinking using facebook_event_checkin?!
  -- anyhow, at 2017 december, of event name SQL Symphony Concert,
  -- and thrice (GROUP BY person_id HAVING count = 3)
  SELECT *, COUNT(*) AS count
  FROM facebook_event_checkin
  WHERE event_name = 'SQL Symphony Concert'
    AND date >= 20171201
    AND date <= 20171231
  GROUP BY person_id
  HAVING count = 3
),
employer AS (
  SELECT person.*
  FROM person
    JOIN employer_driver ON person.license_id = employer_driver.id
    JOIN employer_symphony ON person.id = employer_symphony.person_id
)
SELECT *
FROM employer