Introduction To Database Questions and Answers

Answer: B

Correct answer: Binary

A relationship’s degree is the number of entity types it connects: binary for two, unary (recursive) for one entity type related to itself, ternary for three. Binary relationships are much the most common.

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: 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: D

Correct answer: All of the above

A view gives all three. Security: users can be granted access to the view and not to the underlying table, so they see only certain rows or columns. Derived columns: a view can compute values that are not stored. Simplicity: a complex join can be defined once and then queried as though it were a single table.

Answer: B

Correct answer: Naïve users.

Naive (or parametric) users interact through a prepared interface - menus, forms, a screen with a few fields - and never write a query. A bank teller is the standard example. Sophisticated users write their own SQL; stand-alone users work with a personal database of their own.

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: B

Correct answer: Total and partial

Participation is total when every entity of the set must take part in the relationship - every loan must have a borrower - and partial when only some need to. In an E-R diagram total participation is drawn with a double line.

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: 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: C

Correct answer: Relational algebra

Relational algebra is the procedural set of basic operations - selection, projection, union, set difference, Cartesian product, and the joins and intersection derived from them. Relational calculus is the non-procedural counterpart: it describes what is wanted rather than how to compute it, and the two have equivalent expressive power.