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Database Processing
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Businesses of every size organize data records into collections called databases. At one
extreme, small businesses use databases to keep track of customers; at the other extreme,
huge corporations such as Dell and Amazon.com use databases to support complex sales,
marketing, and operations activities. In between, we have businesses like FlexTime that use
databases as a crucial part of their operations, but they don’t have a trained and experienced
staff to manage and support the databases. To obtain answers to the one-of-a-kind queries he
needs, Neil needs to be creative and adaptable in the way that he accesses and uses his
database.
Users have a crucial role in the development of database applications. Specifically, the
structure and content of the database depends entirely on how users view their business
activity. To build the database, the developers will create a model of that view using a tool
called the entity-relationship model. You need to understand how to interpret such models,
because the development team might ask you to validate the correctness of such a model
when building a system for your use. Finally, we describe the various database administration
tasks.
What Is the Purpose of a
Database?
• Purpose: to keep track of things
• If structure of a list is simple, i.e., one theme,
no need to use database technology (video)
Form for Recording Multiple
Themes
General Rule
• Lists of data involving a single theme can be
stored in a spreadsheet.
• Lists that involve data with multiple themes
require a database.
Database
• Database:
 A self-describing collection of integrated
records
 In databases, bytes are grouped into
columns, such as Student Number and
Student Name. Columns are also called
fields. Columns or fields, in turn, are
grouped into rows, which are also called
records.
Characters, Fields, and Records
Hierarchy of Data Elements
Metadata Describes Structure of
Database
Components of a Database
What Are Relationships Among
Rows?
First row of the Email Table is
related to Andrea Baker in
Student Table
Last row in Office_Visit Table
related to Adam Verberra in
Student Table
Relationship Special Terms
• Key – Primary Key
 A column or group of columns that identifies a unique row in
a table.
 Student Number is the key of the Student table. Given a
value of Student Number, you can determine one and only
one row in Student. Only one student has the number 1325.
 Every table must have a key.
 Sometimes more than one column is needed to form a
unique identifier. In a table called City, for example, the key
would consist of combination of columns (City, State).
 Email_Num is the key of Email Table.
 VisitID is the key of Office_Visit Table.
Relationship Special Terms
• Foreign keys
 These are primary keys of a different
(foreign) table than the table in which they
reside.
• Relational databases
 Relationships among tables are created by
using foreign keys.
• Relation
 Formal name for a table
Metadata
• Database:
 A database is a
self-describing
collection of
integrated
records.
• Metadata
 Data that
describe data
Components of a Database
Application System
• Applications make database data more accessible and useful.
• Users employ a database application that consists of forms,
formatted reports, queries, and application programs.
• Database management system (DBMS) processes database
tables for applications.
What Is a Database Management
System (DBMS)?
• DBMS
 A program (software) used to create, process, and administer
a database
• Companies license DBMS products from vendors:
 IBM, Microsoft, Oracle, and others
• Popular DBMS products are:
 DB2 from IBM
 Access and SQL Server from Microsoft
 Oracle from the Oracle Corporation
 MySQL—an open-source DBMS product that is license-free
for most applications
Creating the Database and Its
Structures
• Database developers use the DBMS to create and modify tables,
relationships, and other structures in the database.
• Below, the developer has added a new column called
Response?. This new column has data type Yes/No.
Processing the Database
• DBMS operations
 Read, insert, modify, delete data
 Applications call DBMS in different ways
• From a form, when the user enters new or
changed data, a computer program behind the
form calls the DBMS to make the necessary
database changes.
• From an application program, the program calls
the DBMS directly to make the change.
Structured Query Language (SQL)
• SQL—“see-quell”
• International standard language for creating
databases and database structures, and processing
databases
• All five of the most popular DBMS products accept
and process SQL.
• Following SQL statement inserts a new row into the
Student table:
INSERT INTO Student
([Student Number], [Student Name], HW1, HW2, MidTerm)
VALUES
(1000, ’Franklin, Benjamin’, 90, 95, 100);
Administering the Database
• DBMS provides tools to assist in administration of the
database.
• Used to set up a security system involving user
accounts, passwords, permissions, and limits for
processing the database
• Backing up database data, adding structures to
improve performance of database applications,
removing data no longer wanted or needed, and
similar tasks
• Most organizations dedicate one or more employees
to the role of database administration.
Major Responsibilities of
Database Administration
What Are Forms, Reports, and
Queries?
Reports show data in a
structured context.
What Are Forms, Reports, and
Queries?
Sample query
form used
to enter
phrase for
search
Sample query results of query operation
Why Are Database Application
Programs Needed?
• Forms, reports, and queries work well for standard
functions. However, most applications have unique
requirements that a simple form, report, or query
cannot meet.
• Application programs process logic that is specific to
a given business need.
• Application programs serve as an intermediary
between the Web server and database.
 Responds to events, such as when a user presses
a submit button; also reads, inserts, modifies, and
deletes database data
Four Database Application
Programs Running on a Web
Server Computer
Multi-User Processing Problem
• Lost-update problem
 Process A reads a customer record from a file containing account
information, including the customer’s account balance and phone
number.
 Process B now reads the same record from the same file so it has
its own copy.
 Process A changes the account balance in its copy of the customer
record and writes the record back to the file.
 Process B—which still has the original stale value for the account
balance in its copy of the customer record—updates the customer’s
phone number and writes the customer record back to the file.
 Process B has now written its stale account balance value to the file,
causing the changes made by process A to be lost.
(Source: http://en.wikipedia.org/wiki/File_locking)
Enterprise DBMS vs. Personal
DBMS
• Enterprise DBMS
•
 Process large organizational and workgroup databases
 Support many, possibly thousands, of users and many different
database applications
 Support 24/7 operations and can manage databases that span
dozens of different magnetic disks with hundreds of gigabytes or
more of data
 IBM’s DB2, Microsoft’s SQL Server, and Oracle’s Oracle are
examples of enterprise DBMS products.
Personal DBMS
 Designed for smaller, simpler database applications
 Used for personal or small workgroup applications that
involve fewer than 100 users (normally fewer than 15), single
user
Access: A DBMS and an
Application Development Product
Before building a database, developers construct a logical
representation of database data called a data model to describe the
data and relationships to be stored in database.
Database Development Process
(video link needed)
What Is the Entity-Relationship
Data Model?
• Entity-relationship (E-R) data model
 A tool for constructing data models
 Developers use it to describe the content of a data
model by defining entities that will be stored in
database and relationships among those entities
 Unified Modeling Language (UML), less popular,
tool for data modeling
Entities
• Some thing that the users want to track
• Examples of entities:
 Order, Customer, Salesperson, and Item. Some entities represent a
physical object, such as Item or Salesperson; others represent a
logical construct or transaction, such as Order or Contract.
 Entity names are always singular.
• Attributes
 Describe characteristics of an entity.
 Examples: order attributes are OrderNumber, OrderDate, SubTotal,
Tax, Total, and so forth.
• Identifier
 An attribute (or group of attributes) whose value is associated with
one and only one entity instance.
Student Data Model Entities
Entities with Relationships
Sample Relationship (Version 1)
Crow’s
Feet
1:N
N:M
1:N = many-to-many
relationships
N:M = many-to-many
relationships
One department can have
many advisers, but an adviser
has at most one department.
One adviser can have many
students and one student can
have many advisers.
Sample Relationships (Version 2)
Advisers may advise in more than one department, but a
student may have only one adviser, representing a policy that
students may not have multiple majors.
Crow’s-Foot Diagram Version
Maximum cardinality—maximum number of entities that can be
involved in a relationship. Vertical bar on a line means that at least one
entity of that type is required.
Minimum cardinality—minimum number of entities that can be involved
in a relationship. Small oval means that the entity is optional; the
relationship need not have an entity of that type.
Database Design
• Database design is the process of converting a data
model into tables, relationships, and data
constraints.
• Database design team transforms entities into tables
and expresses relationships by defining foreign keys.
• Two important database design concepts:
normalization and the representation of two kinds
of relationships.
• Normalization is a foundation of database design.
• Representation of relationships will help you
understand important design considerations.
Normalization
Normalization is the process of converting a poorly structured table into
two or more well-structured tables. Problem with these tables, have two
independent themes: employees and departments.
Data Integrity Problems
• In previous figure, some rows show Dept. 100 is “Accounting and
Finance” and others show Dept. 100 is “Accounting.” Which one
is correct?
• A table with data integrity problems will produce incorrect results
and inconsistent information.
• Data integrity problems happen when data are duplicated.
• Users will lose confidence in the information, and system will
develop a poor reputation. Information systems with poor
reputations become serious burdens to the organizations that
use them.
Normalizing for Data Integrity
• Normalized tables eliminate data duplication,
but they can be slower to process.
• General goal of normalization is to construct
tables such that every table has a single topic
or theme.
Normalizing for Data Integrity
• The way to correct the problem is to split the table into two
tables, each with its own theme.
Summary of Normalization
• Database practitioners classify tables into various
normal forms according to the kinds of problems they
have.
• Transforming a table into a normal form to remove
duplicated data and other problems is called
normalizing the table.
• Normalization is just one criterion for evaluating
database designs. Normalized designs can be slower
to process, database designers sometimes choose to
accept nonnormalized tables. The best design
depends on the users’ processing requirements.
Representing Relationships
Representing
a 1:N
Relationship
Representing an N:M
Relationship
Data Aggregators
• Laws that limit the data that federal and other
governmental agencies can acquire and store.
• Some legal safeguards on data maintained by credit
bureaus and medical facilities.
• No such laws that limit data storage by most
companies (nor are there laws that prohibit
governmental agencies from buying results from
companies like Acxiom.
How Will this Change by 2020?
• Absent any public outcry for legislation to limit such
activity, aggregator data storage will continue to grow
exponentially and companies will have even more
data about you, the state of your health, your wealth,
your purchase habits, your family, your travel, your
driving record, and, well, anything you do.
• Query, reporting, and data mining technology will
improve and Moore’s law will make computer
operations that are too slow to be practical today,
feasible tomorrow.
• The picture of you will become more and more
detailed.
Why Do You Care?
• Data could be stolen and used for criminal
activity against you.
• Data might not be accurate.
• No organization is required by law to tell you
the data that it stores about you and what it
does with it.
What If…
• You enroll in a “healthy eaters” medical insurance
program, similar to “safe drivers” auto insurance.
Your premiums are lower because you eat well,
except that the insurance company notes from
last month’s data that you bought four large
packages of Cheetos, and your health insurance
premium is increased, automatically. You have
no idea why.
• Could this actually happen – or something like
this?