Introduction To Database Questions and Answers

Answer: D

Correct answer: All of above

All three are among the reasons for using a DBMS: data independence, so storage can change without rewriting applications; centralised control, so standards, security and backup are managed in one place; and controlled redundancy, so the same fact is not stored in several places and allowed to drift out of step.

Answer: C

Correct answer: Data Structure

At bottom a database is a data structure - an organised arrangement of data with defined relationships - but a complex one, built from tables, indexes, keys and metadata, and large enough to need software of its own to manage it.

Answer: B

Correct answer: metadata

USER_TABLES describes the structure of the database - table names, column counts, keys - not the data the organisation stores. That is metadata, kept in the system catalogue and queryable with ordinary SQL, which is exactly what makes a database self-describing.

Answer: A

Correct answer: Tuple.

In relational terminology a row is a tuple, a column is an attribute, the table itself is a relation, the number of attributes is its degree and the number of tuples its cardinality.

Answer: B

Correct answer: multiuser database application

An ERP system runs a whole organisation - finance, stock, payroll, orders - with many people working in it at once, so it is a multi-user application. That is what brings in concurrency control, locking and transaction management.

Answer: D

Correct answer: both B and C

Data independence has two halves: physical independence means programs do not depend on how the data is stored, and logical independence means they survive changes to the logical structure. Both are meant by the term, which is why the two options are taken together.

Answer: B

Correct answer: False

Applications interact with the DBMS, not with the database. Only the DBMS reads and writes the stored data, which is what allows it to enforce integrity constraints, manage concurrent access and keep the physical storage independent of the applications above it.

Answer: D

Correct answer: COBOL programs

The basic elements are users, database applications, the DBMS and the database. A COBOL program is merely one possible way of writing an application - a language choice, not an element of the architecture.

Answer: A

Correct answer: Cartesian product

The Cartesian product \(R_1 \times R_2\) pairs every tuple of one relation with every tuple of the other, so the result has all the attributes of both and \(m \times n\) tuples. Difference and intersection require the two relations to be union-compatible and produce no new attributes at all.

Answer: A

Correct answer: Network Model

The set is the central construct of the CODASYL network model: a named one-to-many relationship between an owner record type and a member record type, navigated by following pointers. The relational model replaced it with matching key values, and the hierarchical model used parent-child trees.