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.
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 |
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