Database question:

Explain each of the following terms in a relational model: (i) Candidate key (ii) Domain (b) What is the referential integrity in a relational model? Explain why it is desirable to enforce the rule in a relational database. (c) A conceptual data model in ER diagram is given below: (i) Describe the relationship Publishes in terms of its degree and type. (ii) Describe how to resolve the many-to-many relationship Writes for a relational database. (iii) Map the conceptual data model into a relational schema, i.e. a logical model for relational databases. (iv) Write an SQL statement to list the number of textbooks published each year in UK in a descending order of the numbers