Introduction To Database Questions and Answers

Answer: A

Correct answer: External

The three-level architecture runs external → conceptual → internal. The external level is closest to the user: each user group sees its own view of the data. The conceptual level is the whole database as one community picture, and the internal level describes how it is physically stored.

Answer: C

Correct answer: View never contains derived columns.

That statement is false: a view may perfectly well define computed columns, such as price * quantity AS total, and doing so is one of its common uses. The other three are true - a view is derived from other tables, it is virtual in the sense that it stores no rows, and its definition is stored permanently in the system catalogue.

Answer: B

Correct answer: False

Oracle is ranked the hardest to use, not the easiest - the price of being the most capable and most configurable. Microsoft Access is the easiest of the products discussed, and correspondingly the most limited.

Answer: C

Correct answer: Attributes

The properties of an entity are its attributes - a student’s roll number, name and date of birth. In the implemented database they become the columns of a table.

Answer: A

Correct answer: True

SQL is an international standard, maintained by ANSI and ISO, and every commercial relational DBMS implements it. The qualification worth knowing is that each product adds extensions and differs in the corners, so a complex query is not always portable unmodified - but the core language is common ground.

Answer: D

Correct answer: Diamond

In the standard E-R notation, a diamond is a relationship type, a rectangle an entity set, and an ellipse an attribute. A double diamond marks the identifying relationship of a weak entity.

Answer: D

Correct answer: Oracle Corporation's Oracle

Oracle is the hardest of the four to use, and for a reason: it is the most configurable and the most capable at scale, so it exposes far more to be administered - tablespaces, instances, tuning parameters. Access sits at the other end, easy to use and correspondingly limited.

Answer: B

Correct answer: Data elements in the database can be modified by changing the data dictionary.

The dictionary describes the data; it does not contain it. Editing the description does not change the stored values - changing an element means altering the data itself, through the DBMS. The other three statements are true: the DBA maintains it, it holds the name and description of every element, and it is primarily the DBA’s tool.

Answer: D

Correct answer: Not a value

NULL means that a value is missing, unknown or not applicable. It is emphatically not zero or a blank string, both of which are perfectly definite values. The consequence is that comparisons with NULL yield unknown rather than true or false, which is why x = NULL never matches and IS NULL must be used instead.

Answer: C

Correct answer: File Management System

Before database systems, applications kept their data in ordinary files, each written for one program. The resulting problems - the same data duplicated in several files, inconsistency between them, and applications that broke when a layout changed - are what the database approach was created to solve.