placesOfInterestPairs

My solution:

CREATE PROCEDURE placesOfInterestPairs() 
BEGIN 
  SELECT place1, 
         place2 
  FROM   (SELECT sights.name                          AS place1, 
                 sights2.name                         AS place2, 
                 SQRT(POW(sights.x - sights2.x, 2) 
                      + POW(sights.y - sights2.y, 2)) AS distance 
          FROM   sights, 
                 sights AS sights2 
          WHERE  sights.name < sights2.name) AS t 
  WHERE  distance < 5 
  ORDER  BY place1, 
            place2; 
END 

userCountries

My solution:

CREATE PROCEDURE userCountries() 
BEGIN 
  SELECT id, 
         country 
  FROM   users, 
         cities 
  WHERE  users.city = cities.city 
  UNION 
  SELECT DISTINCT id, 
                  "unknown" AS country 
  FROM   users, 
         cities 
  WHERE  users.city NOT IN (SELECT city 
                            FROM   cities) 
  ORDER  BY id; 
END 

scholarshipsDistribution

My solution:

CREATE PROCEDURE scholarshipsDistribution() 
BEGIN 
  SELECT candidate_id AS student_id 
  FROM   candidates 
  WHERE  candidate_id NOT IN (SELECT DISTINCT candidate_id AS id 
                              FROM   candidates, 
                                     detentions 
                              WHERE  candidate_id = student_id 
                              ORDER  BY candidate_id); 
END