Exam 1

Question 1

Data

Answer 1

Raw facts that need to be processed and could be simple: numbers text

Question 2

Information

Answer 2

Data that has been processed, organized and presented in a useful way

Question 3

Traditional db

Answer 3

Data elements or fields are text or numbers

Question 4

Modern db

Answer 4

Fields can be images, videos, and sounds

Question 5

Entity

Answer 5

Name things, people or objects that it represents

Question 6

DBMS

Answer 6

DataBase Management System

Makes it easier to: define a database, construct it, maintain and manipulate it, and give access to a variety of users/applications

Question 7

Record

Answer 7

Another name for the row of a table

Question 8

Database Catalog

Answer 8

A file containing all definitions and constraints of data and database, such as definition of each table, each column data type and its value constraint.

Question 9

Virtual data

Answer 9

Data not explicitly stored in database, such as GPA

Question 10

Data normalization

Answer 10

Removing redundancy

Question 11

Correct database state

Answer 11

DBMS provides recovery functionality that, on a system crash, will go back to the last persistent state

Question 12

End user

Answer 12

Those who use databases on a daily basis and for their job. The db application is for them. Examples: bank tellers, cashiers

Question 13

Database Administrators

Answer 13

Defining users, setting access levels

Question 14

Data Abstraction

Answer 14

Removing unnecessary details and highlighting essential features to understand data better, for the purpose of developing a database application.

Question 15

Database Schema

Answer 15

it is the description of a database, you specify it in database design phase and it does not change much after that.

Stored as metadata in catalog file in DBMS and includes structure of the db and all constraints that keep the database valid.

Question 16

Schema Diagram

Answer 16

Representing the database schema description as a diagram

Question 17

Database state/snapshot

Answer 17

Data in a database at a particular moment in time

Question 18

Three-Schema Architecture

Answer 18

Introduced in 1978 to support data independence between user applications and the physical database.

External level: End-user views; what ordinary staff see

Conceptual level: Represents database in terms of tables, attributes, data types, relationships and constraints

Internal level: Uses a physical data model to describe details of storing/retrieving data in disk level

o In internal level; a sequence of numbers (bytes) is read from disks.
o In conceptual level; that is in terms of table(s) of grades, student_info, course_info, etc.
o In external level; you see a nicely formatted human readable form containing all your courses and grades.

Question 19

Data Independence

Answer 19

The capacity to change database schema in one level without having to change the higher level schemas

Question 20

Data Definition Language

Answer 20

Used by the DBA to specify the conceptual schema of a database; also used to define internal and external schemas.

Question 21

Data Manipulation Language

Answer 21

Used to specify database retrievals, updates, and can be embedded in a programming language like Java or C#. (JDBC/OBDC)
DMLs can be high level or low level

Question 22

Data Dictionary

Answer 22

A file similar to the catalog file and has all catalog file information. It is for humans and it could include comments and descriptions as well

Question 23

Client-Server Architecture

Answer 23

Client: User machine which provides the user interface and local processing

Server: A strong machine having hardware and software to provide different services to clients

Question 24

Categories of DBMS

Answer 24

Centralized - Everything is included into one machine; both DBMS software and GUI applications

Client-server architecture - Server machine has the DBMS software, and clients have web access or form based software

Question 25

Parametric users

Answer 25

End users with a few defined commands to interact with DBMS, such as bank tellers

Question 26

Privileged commands

Answer 26

Commands such as altering tables, changing data types, defining users, etc. that just DBAs have privilee to run

Question 27

Canned Transactions

Answer 27

Pre-programmed and fully tested transactions for non-IT personnel, these transactions cannot harm the system

Question 28

Runtime database processor

Answer 28

Runs transactions on a stored database, and gets information such as data types and constraints from catalog files to do so

Question 29

Stored data manager

Answer 29

It manages buffers, read/write on disks and moving data to RAM

Question 30

DBMS Classifications

Answer 30

- Based on data models: o Relational, Object-oriented, key-value storage (NOSQL). - Other classification: o Centralized vs. client-server based. o Single user vs. multi user

Question 31

Attribute Types

Answer 31

Simple - Hold one value Composite - Composed of several simple attributes (Name) Multivalued attributes - Hold multiple values

Question 32

Derived Attribute

Answer 32

An attribute that doesn't need to be stored in a db, but you can retrieve it via query and based on other stored attributes. Shown by dotted circle Example: GPA

Question 33

Weak Entity

Answer 33

Has no key attribute of its own. Owner entity type: weak entity instances are identified by being related to a strong entity instance, that strong entity type is called owner entity type (or parent entity type). Identifying relationship: the relationship which relates a weak entity type to its owner is called this! partial key: an attribute of a weak entity type which uniquely identifies an instance, among instances of the same owner entity. o In ER, it is underlined with a dashed line. A weak entity type always has a total participation constraint (existence dependency) with respect to its identifying relationship. o A weak entity cannot be identified without an owner entity.

Question 34

Relational Model

Answer 34

A data model which represents all data in terms of tuples, and groups tuples as relations. Majority of DBMS software is based on the relational model. Table row = record = tuple Relation can be represented as a table

Question 35

Key of a Relation

Answer 35

An attribute that can identify a row uniquely. Also just known as a key

Question 36

Schema of a Relation

Answer 36

Denoted by R(A1, A2...) where R is the name of the relation, A1 and A2 are attributes. Example: CUSTOMER(Cust-id, Cust-name)

Question 37

Tuple

Answer 37

An ordered set of values, each derived from an appropriate domain.

Question 38

Inherent/Implicit Constraints

Answer 38

Based on the data model itself. Example: RM doesn't allow a list as a value for an attribute

Question 39

Schema-based or Explicit Constraints

Answer 39

Beyond the expressive power of the model and must be specified and enforced by the application programs

Question 40

Constraints

Answer 40

Conditions that must be held on all valid relation states. Three types: Key constraints Entity integrity constraints Referential integrity constraints Domain constraint

Question 41

Key Constraints

Answer 41

Superkey of R such that no two tuples in any valid relation state will have the same value

Question 42

Entity Integrity

Answer 42

Primary key attributes cannot have null values in any tuple, since they're used as identifiers.

Question 43

Referential Integrity

Answer 43

A tuple in the relationship reference no longer exists or can no longer be accessed

Question 44

Semantic Constraints

Answer 44

Based on application semantics and cannot be expressed by the model. Example: "the maximum number of hours per employee for all projects he or she works on is 56 hours per week"