Write SQL queries for the LIBRARY database queries given in Exercise 6.18. How can the key and foreign key constraints be enforced by the DBMS? Is the enforcement technique you suggest difficult to...

Write SQL queries for the LIBRARY database queries given in Exercise 6.18.

How can the key and foreign key constraints be enforced by the DBMS? Is the

enforcement technique you suggest difficult to implement? Can the constraint

checks be executed efficiently when updates are applied to the database?