1. What is an Entity?

It is a 'thing' in the real world with an independent existence.

2. What is DDL Interpreter?

It interprets DDL statements and record them in tables containing metadata.

3. What is 2NF?

A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

4. What do you mean by atomicity and aggregation?

Atomicity :  Either all actions are carried out or none are. Users should not have to worry about the effect of incomplete transactions. DBMS ensures this by undoing the actions of incomplete transactions.

Aggregation :   A concept which is used to model a relationship between a collection of entities and relationships. It is used when we need to express a relationship among relationships.

5. What is degree of a Relation?

It is the number of attribute of its relation schema.

6. What is an attribute?

It is a particular property, which describes the entity.

7. Define the "integrity rules"

There are two Integrity rules.

Entity Integrity : States that “Primary key cannot have NULL value”

Referential Integrity : States that “Foreign Key can be either a NULL value or should be Primary Key value of other relation.

8. What is Multivalued dependency?

Multivalued dependency denoted by X Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties

•  t3[x] = t4[X] = t1[X] = t2[X]
•  t3[Y] = t1[Y] and t4[Y] = t2[Y]
•  t3[Z] = t2[Z] and t4[Z] = t1[Z]

where [Z = (R-(X U Y)) ]

9. What is Functional Dependency?

A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

10. What is an Entity set?

It is a collection of all entities of particular entity type in the database.