Final answer:
The question involves writing relational algebra queries to find: a) cities where salaries can buy a locally made car, b) car pairs within a specified budget, and c) manufacturers selling cars of at least three different colors.
Step-by-step explanation:
The question asks for relational algebra queries for three specific scenarios involving the relations Car(model, price, color, manufacturer), Manufacturer(name, city), and Salary(city, salary). While the SQL code is not provided, an understanding of relational algebra is needed to conceptualize the data manipulations required to answer such database queries.
a) To find all cities where 24 salaries can buy a locally made car, you would need to aggregate salaries in each city, compare it to the prices of cars made by manufacturers in the same city, and return those cities where the total salary is sufficient to buy a car.
- b) To find all pairs of cars such that one is blue and the other is red and within a certain budget X, you would perform a Cartesian product on the Car relation filtered for red and blue cars, then select pairs whose combined price is less than or equal to X.
- c) To find all manufacturers that sell cars of at least three different colors, you would group Car relation by manufacturer, count the distinct colors, and then select those manufacturers with a count of three or more.