(a) Outline four Data Definition Language statements used in Structured Query Language. (4 marks) (b) Explain three characteristics of relational databases (6 marks) (c) Distinguish between domain constrain and referential integrity constraint as used in database design. (4 marks) (d) A database has a relation named Students Details with fields: Names. AdNumber and Class. (i) Explain the output from each of the following algebraic expression from the relation: L 8 (StudentsDetails) II. Name, Class (StudentsDetails) (4 marks) (ii) Write the algebraic expression for the Structured Query Language statement: (2 marks) select count(salary) from StudentsDetails;