Problem: The airline has decided that economy class passengers should not get meals on board short haul flights. Write a stored function that takes flight number and meal code ('ST' or 'VG') as input, and returns the number of meals (of that type) required on board the flight. The function should also return 0 if there are no tickets sold yet for the specified flight. For the execution, write a select statement to produce a table that gives the number of meals of each type that are required so far for each flight in the database.