Which of the following operations need the participating relations to be union compatible ?
UNION
INTERSECTION
SET DIFFERENCE
All of the above
An instance of relational schema R (A,B,C) has distinct values of A including NULL values. Which one of the following is true?
A is a candidate key
A is not a candidate key
A is a primary key
Both a and c
In the abstraction of a database system the external level is the
physical level
logical level
conceptual level
view level
How many distinct tuples are there in a relation instance with cardinality 22 ?
22
11
1
none
Related fields in a database are grouped to form a
data file
data record
menu
bank
In a relational model, relations are termed as
tuples
attributes
tables
rows
Which of the following operations is used if we are interested only in certain columns of a table ?
PROJECTION
SELECTION
SELECT
Which database level is closest to the users?
external
internal
physical
conceptual
Who is responsible for managing and controlling the activities associated with the database ?
Database administrator
Programmer
Naive user
End user
Cartesian product in relational algebra is
a unary operator
a binary operator
a ternary operator
not defined