Some questions about database

Question 22

1. _______ execution of transactions means that transactions are performed one after another, without any interleaving of operations.

	A.	Scheduled
	B.	Concurrent
	C.	Serial
	D.	Precedence

Question 24

1. When converting an E-R model to a relational model, the table for a binary relationship can be replaced by a foreign key provided the relationship is not

	A.	many-to-many
	B.	many-to-one
	C.	one-to-many
	D.	one-to-one

Question 27

1. In the EE-R model, if entity instances can belong to more than one subclass in a specialization, the subclasses are

	A.	incorrect
	B.	disjoint
	C.	overlapping
	D.	complete

0.5 points

Question 28

1. Since the result of an SQL SELECT statement can have duplicates, the result is referred to as

	A.	a set
	B.	a relation
	C.	a multi-set
	D.	a table

Question 31

1. In the E-R model, an attribute that can be broken down into smaller attributes is called

	A.	composite
	B.	null
	C.	a superattribute
	D.	derived

0.5 points

Question 32

1. The Oracle tool that can be used to control backup and recovery is

	A.	JDBC
	B.	RMAN
	C.	SQL*Plus
	D.	PL/SQL

Question 34

1. In the EE-R model, completeness constraints tell us whether a specialization is

	A.	total or partial
	B.	union or category
	C.	disjoint or overlapping
	D.	predicate-defined or user-defined

0.5 points

Question 35

1. Code example 6-1 SELECT vendor_name, COUNT(*) AS number_of_invoices, MAX(invoice_total - payment_total - credit_total) AS balance_due FROM vendors v JOIN invoices i ON v.vendor_id = i.vendor_id WHERE invoice_total - payment_total - credit_total > (SELECT AVG(invoice_total - payment_total - credit_total) FROM invoices) GROUP BY vendor_name ORDER BY balance_due DESC

(Please refer to code example 6-1.) When this query is executed, the number_of_invoices for each row will show the number

	a.	1
	b.	of invoices for each vendor
	c.	of invoices in the Invoices table
	d.	of invoices for each vendor that have a larger balance due than the average balance due for all invoices

Question 38

1. When an entity set is related to itself, we have a _______ relationship.

	A.	extended
	B.	optional
	C.	mandatory
	D.	recursive

0.5 points

Question 39

1. In the relational model, the table in which a foreign key appears as the primary key is called its

	A.	root relation
	B.	home relation
	C.	child relation
	D.	foreign relation