How many stops are in the database.

SELECT COUNT(*) FROM stops;

Find the id value for the stop 'Craiglockhart'

SELECT id, name FROM stops WHERE name = 'Craiglockhart';

How many stops are there on the '4' 'LRT' service.

SELECT COUNT(DISTINCT stop) FROM route
  WHERE num = '4' AND company = 'LRT';

Obtain a list of the stops on the 'LRT' route '4'

1. In route order

   SELECT name FROM route, stops
     WHERE num = '4' AND company = 'LRT'
       AND stop=id
     ORDER BY pos;

2. In alphabetical order

   SELECT name FROM route, stops
     WHERE num = '4' AND company = 'LRT'
       AND stop=id
     ORDER BY name;

Give the services which pass through 'Craiglockhart'

SELECT num, company FROM stops, route
  WHERE name = 'Craiglockhart' AND id = stop;

Give a list of all the services which connect stops 115 and 191. ('Haymarket' and 'Portabello')

SELECT R1.num, R1.company FROM route R1, route R2
  WHERE R1.stop = 115 AND R2.stop=191 
    AND R1.num=R2.num AND R1.company=R2.company;

Give a list of the services which connect the stops 'Craiglockhart' and 'Tollcross'

SELECT R1.num, R1.company FROM route R1, route R2, stops S1, stops S2
  WHERE R1.stop = S1.id AND R2.stop=S2.id 
    AND R1.num=R2.num AND R1.company=R2.company
    AND S1.name = 'Craiglockhart' AND S2.name = 'Tollcross';

Give a list of the stops which may be reached from 'Craiglockhart' by taking one bus. Include the details of the appropriate service.

SELECT R1.num, R1.company, S2.name FROM route R1, route R2, stops S1, stops S2
  WHERE R1.stop = S1.id AND R2.stop = S2.id 
    AND R1.num=R2.num AND R1.company=R2.company
    AND S1.name = 'Craiglockhart';

Show how it possible to get from Sighthill to Craiglockhart.

You might intersect all the places from Craiglockhart with all the places from Sighthill. This would at least be a start.

SELECT S2.name FROM route R1, route R2, stops S1, stops S2
  WHERE R1.stop = S1.id AND R2.stop = S2.id 
    AND R1.num=R2.num AND R1.company=R2.company
    AND S1.name = 'Craiglockhart'
INTERSECT
SELECT S2.name FROM route R1, route R2, stops S1, stops S2
  WHERE R1.stop = S1.id AND R2.stop = S2.id 
    AND R1.num=R2.num AND R1.company=R2.company
    AND S1.name = 'Sighthill';