Some questions about database Question 22 1. _______ execution of transactions m
ID: 3730582 • Letter: S
Question
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
A.
Scheduled
B.
Concurrent
C.
Serial
D.
Precedence
Explanation / Answer
Answer 1
B. Serial , It is a schedule in which transactions are adjusted such that one exchange is executed first. At the point when the main exchange finishes its cycle, at that point the following exchange is executed. Transactions are requested consistently. This kind of schedule is known as a serial schedule, as transactions are executed in a serial way.
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