1. What is a view? How it is related to data independence?

A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table. In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary.
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the effects of restructuring and growth in the database. Hence accounts for logical data independence.

2. What is 5NF?

A Relation schema R is said to be 5NF if for every join dependency {R1, R2, ..., Rn} that holds R, one the following is true

•  Ri = R for some i.
•  The join dependency is implied by the set of FD, over R in which the left side is key of R.

3. What is a checkpoint and When does it occur?

A Checkpoint is like a snapshot of the DBMS state. By taking checkpoints, the DBMS can reduce the amount of work to be done during restart in the event of subsequent crashes.

4. What is Query evaluation engine?

It executes low-level instruction generated by compiler.

5. What is SDL (Storage Definition Language)?

This language is to specify the internal schema. This language may specify the mapping between two schemas.

6. Brief theory of Network, Hierarchical schemas and their properties

Network schema uses a graph data structure to organize records example for such a database management system is CTCG while a hierarchical schema uses a tree data structure example for such a system is IMS.

7. How is the data structure of System R different from the relational structure?

Unlike Relational systems in System R

•  Domains are not supported
•  Enforcement of candidate key uniqueness is optional
•  Enforcement of entity integrity is optional
•  Referential integrity is not enforced

8. What is Relationship set?

The collection (or set) of similar relationships.

9. What is 4NF?

A relation schema R is said to be in 4NF if for every Multivalued dependency X Y that holds over R, one of following is true

•  X is subset or equal to (or) XY = R.
•  X is a super key.

10. What are partial, alternate,, artificial, compound and natural key?

Partial Key  :   It is a set of attributes that can uniquely identify weak entities and that are related to same owner entity. It is sometime called as Discriminator.

Alternate Key :   All Candidate Keys excluding the Primary Key are known as Alternate Keys.

Artificial Key :   If no obvious key, either stand alone or compound is available, then the last resort is to simply create a key, by assigning a unique number to each record or occurrence. Then this is known as developing an artificial key.

Compound Key :   If no single data element uniquely identifies occurrences within a construct, then combining multiple elements to create a unique identifier for the construct is known as creating a compound key.

Natural Key :   When one of the data elements stored within a construct is utilized as the primary key, then it is called the natural key.