Transcript Chapter 10 - Computer Science Technology

Chapter 9
Database Management
Discovering Computers
Fundamental
Databases
My first suggestion is to read through
the text book.
 Lot’s of information there for you!!!
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Database Definition
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A database is a collection of data
organized in a manner that allows
access, retrieval, and use of that data.
Database Confusion
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When reading the textbook, a database might
look like a spreadsheet. It is NOT a
spreadsheet.
 The word “database” is a generic term.
Similar to the word “file”
– Files can be created with a word processor or a
spreadsheet. A specific word processor software
might be Microsoft Word. A specific spreadsheet
software might be Microsoft Excel
– A database is created using a DBMS tool. A
specific DMBS is Oracle, or Sybase, or Microsoft
Access!
DBMS
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Microsoft Access is a DBMS that you can use
on your computer. It comes in Office 2003. It’s
relatively easy to learn and use.
 Oracle and Sybase are two companies that
make a DBMS. Their DBMS applications are
for larger computers and larger amounts of
data. They are more complicated to learn.
Most companies use one of these two DBMS
applications.
Database Example
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What if HCC wanted to keep a list of
ALL of its students? They don’t want to
type up the list in a word processor or
spreadsheet. If they did that, then they
would have to look through ALL the
students just to find one student. HCC
probably has millions of students.
More on Database Example
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This is when they would use a database.
First, they would pick a specific tool (DBMS)
to create the database. They might pick
Microsoft Access.
 This tool would guide them in entering all
their data.
 The DBMS would then save this information
in a “special” way, that only the DBMS
program could understand.
Database Queries
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If HCC wanted to look up the information for a
particular student, they would HAVE to use
the DBMS tool. They would start the DBMS
tool, tell it what database and table to look at
(the one with the students), and then they
would make a “query”. That is, they would
make a request to retrieve information in the
table.
 The DBMS would display the information.
More on Query
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For example, you could use your DBMS to
say “hey, go get me all the students who live
in Katy”. Or maybe you could say “hey, go get
me all the students who are in ITSC1301”.
 That is a query. However, you wouldn’t just
say “Hey … go get me this”, you would have
to phrase it in a way that the DBMS
understands.
Queries
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In the book they talk about Query-ByExample and Query Languages
 Query-By-Example
– Making a query using the menus of the DBMS
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Query Languages
– A special language you use to “talk” to the
database to make a query
– SQL is a common query language p.348
– SQL is used in most relational databases,
regardless of the DBMS you purchased.
Quick Review
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Think of the DMBS as a software program
with elaborate menus
Some menus let you enter data
Some menus let you retrieve data
Some menus let you change data
All this information gets saved in database
files. You need the DBMS tool to access
those files!!
Not as easy as it sounds
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Database problems:
– More expensive
– More complicated to use
– Require computers with more hardware, memory
and processing power (generally)
I personally wouldn’t use a database to hold
all of my students’ information since I don’t
have that many (between 100-200)
 A database would be more trouble than it’s
worth in my case
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Organizing Data
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Data isn’t kept in a chart, but the data is
organized in that manner.
When you enter data, you generally enter a
record at a time.
A record is a group of related fields (think of it
as a row in a chart)
Each column is really referred to as a field.
A TABLE is a collection of records (think of it
as a chart).
Possible HCC Tables
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If HCC had a database with students
and their grades, they could set it up in
the following tables:
– Admission’s department might have a table
with students, ids, addresses, age, etc…
– Math department might have a table with
students, grades, math courses
– Library might have a table with students
and which books they have checked out
Redundancy
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What if the Math department needed the
student addresses? Well, they could keep the
students’ addresses in their table, but then
the addresses would also be in the science
department’s tables, and the HCC
admission’s tables, etc…
 Instead, the addresses only have to be in one
table (the HCC admission table). If the math
department wants to get the address of a
student, it can just refer to the other table.
 This way the same data doesn’t have to be
kept in 3 different places!!
More on Redundancy
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Using a DBMS and a query, it is very
easy to get information from different
tables:
– Query: hey, get the students from the math
table who are in Algebra, and at the same
time, pull their addresses from the
Admissions table.
DBA
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There is an “art” in selecting how to layout the
databases (how many tables, and what to
include in each table)!!
A DBA is a database administrator.
They set up the database and keep it
functioning.
They use programming
If you have a lot of experience as a DBA you
can make quite a bit of money.
Database Terms
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Data Integrity – how accurate is the data? If
you entered bad data (wrong address), then
the database is useless.
– GIGO: garbage in, garbage out
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Data Security – protecting the data so it isn’t
lost or misused
– (having certain passwords to access database)
– For example, I have no authority to access the
HCC databases.
Database Functions
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Maintaining Data
– Adding data
– Changing data
– Deleting data
– Validating data (making sure that the letter
grades entered were all between A-F … a
G would be an invalid grade)
Information Systems
For some strange reason, Information
Systems is a topic that is covered at the
end of this chapter.
 It is a lead in to chapter 11
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What is an Information System?
First, what is an information system? An
information system is a collection of
hw,sw,data, people, and procedures
designed to generate information that
supports the activities of users in an
organization. So, what does that mean???
 Basically, it's similar to a program, but in a
much larger scale. Sure, you may go to the
store to buy a program/software to play
solitaire, or to do your taxes, or to teach a kid
to read. However, in large companies, they
use more than programs, they use
Information Systems.
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Information System Example?
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Online registration here at HCC
isn't handled by one program, it's
probably handled by an
INFORMATION SYSTEM. Many
things all working together to make
it work.
Different Categories of
Information Systems in Textbook
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In the book they talk about
– OIS (office information systems) – enhances
communications, automates tasks
• Continental Cool Savers is an OIS example … it emails
you whenever special Continental Airfares come out
– TPS (transaction processing systems) –
processing day to day transactions
• HCC student system
• Online banking activity
– Expert Systems (my favorite)
– Others (OIS, DDS, MIS)
Summary
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Understand what a database is
Understand the record versus field concept
Understand some of the terms and functions
Understand the advantages and
disadvantages (as listed in book)
Understand what a query is (query-byexample versus a query language)
Know what a DBMS is versus a database
Know what SQL is
Understand what an Information System is
Know the categories of Information Systems