An attempt at Bacon numbers in SQL by Adomas Boruta. 

I instead of writing recursive selection for Bacon number, 
I wrote a procedure which calculates the distance from some person to all others (-1 being unrelated, 0 is the person itself and positive number is the distance). 
For small database, it took 12m 27s 332ms to complete. 

It requires table:

CREATE TABLE PEOPLE_DISTANCE (
id                INTEGER IDENTITY PRIMARY KEY,
person_id         INT NOT NULL,
related_person_id INT NOT NULL,
distance          INT NOT NULL
);

Procedure:

CREATE PROCEDURE generate_distance_to_person(IN p_id INT)
MODIFIES SQL DATA
  BEGIN ATOMIC
    DECLARE count_var INTEGER;
DECLARE n INTEGER;

BEGIN ATOMIC
      DELETE FROM PEOPLE_DISTANCE
WHERE person_id = p_id;

INSERT INTO PEOPLE_DISTANCE (person_id, related_person_id, distance)
SELECT
          p_id AS person_id,
id   AS related_person_id,
          -1   AS distance
FROM PEOPLE;

UPDATE PEOPLE_DISTANCE SET distance = 0
      WHERE person_id = p_id AND related_person_id = p_id;

SET count_var = 1;
SET n = 0;
WHILE count_var > 0 DO
        UPDATE PEOPLE_DISTANCE SET distance = n + 1
        WHERE person_id = p_id AND related_person_id IN (
SELECT c2.PERSON_ID AS person_id
FROM PEOPLE_DISTANCE
INNER JOIN CREDITS c1 ON PEOPLE_DISTANCE.related_person_id = c1.PERSON_ID
            INNER JOIN CREDITS c2 ON c1.MOVIE_ID = c2.MOVIE_ID
            INNER JOIN PEOPLE_DISTANCE pd ON pd.related_person_id = c2.PERSON_ID
          WHERE
            c1.PERSON_ID <> c2.PERSON_ID
            AND c1.TYPE = 'actor'
            AND c2.TYPE = 'actor'
            AND pd.distance = -1
            AND pd.person_id = p_id
AND PEOPLE_DISTANCE.person_id = p_id
AND PEOPLE_DISTANCE.distance = n
        );

SET count_var = DIAGNOSTICS(ROW_COUNT);
SET n = n + 1;
END WHILE;

END;
END;


And calculation for a person can be performed like this:

CALL GENERATE_DISTANCE_TO_PERSON(107303);

Results can be extracted like this:


SELECT
  person_id,
distance,
count(*) AS total
FROM PEOPLE_DISTANCE
GROUP BY person_id, distance
ORDER BY distance