Introduction To Database Questions and Answers

Answer: A

Correct answer: True

This is the correct chain: users → applications → DBMS → database. Every layer goes through the next, and only the DBMS touches the stored data - which is what allows security, integrity and concurrency to be enforced in one place.

Answer: A

Correct answer: Network Model

The record-based logical models are the relational, network and hierarchical ones - so called because the database is described as a collection of fixed-format records. The E-R model is an object-based (conceptual) model used for design, and the object-oriented model is object-based too.

Answer: C

Correct answer: e-commerce database application

A public shopping site is the standard example of an e-commerce database application: thousands of anonymous users browsing a catalogue and placing orders over the web. It is multi-user too, but e-commerce is the more specific description the question asks for.

Answer: A

Correct answer: True

A database holds both the data and the relationships among it - which orders belong to which customer, which items to which order. Storing the relationships is precisely what distinguishes a database from a collection of separate files or spreadsheets.

Answer: C

Correct answer: All the tuples of R1 and R2

Union returns every tuple that appears in either relation, with duplicates removed. It requires the two to be union-compatible: the same number of attributes, with matching domains. The last option describes an intersection or a join, not a union.

Answer: C

Correct answer: Doubly outlined rectangle

A double rectangle marks a weak entity set - one with no key of its own, whose identity depends on an owner entity. The relationship that connects it to its owner is drawn as a double diamond, and its partial key is underlined with a dashed line.

Answer: A

Correct answer: Database application and the database

The DBMS sits in the middle of the stack: user → database application → DBMS → database. The application never touches the stored data directly; it asks the DBMS, which handles the files, the indexes, concurrency and security. That indirection is what lets the physical storage change without rewriting every application.

Answer: A

Correct answer: PROJECTION

Projection picks out columns - the vertical slice - and removes duplicate rows from the result. Selection is the horizontal counterpart, picking rows that satisfy a condition. In SQL, projection is the list after SELECT and selection is the WHERE clause.

Answer: D

Correct answer: Domain.

A domain is the set of permitted values for an attribute - the integers 0 to 100 for a mark, or a list of valid state codes. Constraining an attribute to its domain is the most basic form of integrity checking a DBMS does.

Answer: B

Correct answer: Microsoft's Access

Access bundles a DBMS with an application generator: forms, reports, queries and macros in the same file as the data. That is what makes it convenient for a small application and unsuitable for an enterprise one, where the DBMS is a separate server and the application is built independently.