2. Database definition
• In general, a database is anything that stores
data
– Example, a phone book which store name &
phone number
• In computer, a database refers to
– collection of organized data to be accessed,
retrieved and used
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3. Function of a database in general
• Allow anyone to:
– store (add)
– delete (remove)
– organize
– use
– present data
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5. What is a DBMS?
• Database Management System is a software
that store and manage database
• It allows to:
• create databases
• insert, update and delete data
• sort and query data
• create forms and reports
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6. Examples of DBMS
• Microsoft Access, MySQL, PostgreSQL, SQL Server,
Oracle, dBASE, Clipper and FoxPro
• Examples of DBMS applications:
Automated teller machine
Computerized Library System
Flight Reservation System
Staff Information System
Students System
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7. DBMS Models
• DBMS Model describe:
– rules and standards on how database organize data
– defines how users view organization of data
• Common models include: (remember)
– Hierarchical model
– Network model
– Object-oriented model
– Relational model
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8. Hierarchical Model
• organizes data in a tree structure
• all access to data starts at the top of the hierarchy
and moves downward
– for example, from customer to orders, vendor to
purchases, etc
• there is a hierarchy of parent and child data
segments
• support one to many relationship
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9. Network Model
• Similar like hierarchical model but
– permit more than one parent per child
– thus permit the modeling of many-to-many relationships in data
• Organizes data using two fundamental constructs, called
records and sets
• Records contain fields , sets define one-to-many
relationships between records: one owner, many
members
• Very flexible
• Not widely use
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10. Object Oriented Model
• based on a collection of objects
• an object contains:
– values stored in instance variables within the object
– bodies of code called methods that operate on the object
• for example, consider an object representing a bank account
– The object contains instance variables number and balance.
– The object contains a method pay-interest which adds interest to the balance.
– Under most data models, changing the interest rate entails changing code in
application programs.
– In the object-oriented model, this only entails a change within the pay-
interest method.
• Diverse structures
• Can execute complex analytical and data manipulation operations
to search and transform multimedia and other complex objects
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11. Relational Model
• Data is stored in two-dimensional tables (rows and
columns)
• Widely used
• Example, Microsoft Access and MySQL
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12. Data Hierarchy
Definition- systematic organization of data, often in a hierarchical
form
Database File Database File: Physical file stored in a storage media.
Example: StudentDB.accdb
Table Table: Contain information on a specific subject / topic.
Example: Student, Courses
Record: Contain information on single data item in a
Record
table. Example: information about a student. Also known
as row in a table.
Field Field: Contain a specific piece of information within a
record. Example: Student Name, Student IC. Also known
as column in a table. 12
14. Relational database
• stores data in tables
• tables are organized into columns, and each
column stores one type of data
• data for a single “instance” of a table is stored as a
row
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15. What is RDBMS?
• RDBMS is a DBMS which manages a relational
database
– Example, Microsoft Access and MySQL
• Data is structured in tables, records and fields
• Each table consists of rows (records)
• Each table row consists of one or more fields
(columns)
• RDBMS store the data into collection of tables,
which might be related by common fields
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16. Advantages of RDBMS
• Minimum data redundancy
• Data consistency - less likelihood of incorrect or
incomplete data being stored or used
• Integrated data – data is organized in logical
relationship thus making it easy to relate data items
• Data sharing – allows users from different department
to share data
• Data accessibility – allows users to access or retrieve
in a flexible manner
• Uniform security, privacy and integrity control – db
administrator can establish control for accessing,
updating and protecting the data
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17. Categories of RDBMS
• Personal database
– Best in single-user environment (up to 10 users)
– Example: Microsoft Access
• Client/Server database
– Support multiple users in a network environment
– Run in a server, client can request data from the server
& query, update & report locally
– Example: SQL Server
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18. Master table
• Contains a primary key (must be unique as a
password)
• Normally is a table that lists the properties of
things that have some permanence and used
many times in other tables
• Example customers, teachers, students and
subjects offered
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19. Transaction table
• Records some kind of interaction or event between
master tables
• Transaction tables are typically used in posting
operations or as lookup tables
• Example,
– In Student Information System, the actual classes taken by
students are transactions because they record specific
interactions between students and teachers
– In an eCommerce software the shopping cart tables are all
transaction tables, they record the purchase of items by
customers
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20. Primary Key
• Field, or fields, which by itself, or together
uniquely identify each row in a table
• Used to match up records in different tables
• Usually indexed
• Help to define the relationships between tables
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21. Primary Key
• Requirement: must be unique and cannot be
empty or null
• Functions:
• Used to associate data from multiple tables
• Prevent duplicate record
• Control the order of records
• Faster to locate records
• Possible to have 2 or more fields as primary key in
a table –this is called composite key
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22. Foreign Key
• Same data field and type which is linked to a
primary key in a corresponding table
• Example:
– In SalesTransaction table below, CustomerID would be the
Foreign Key field
– The Foreign Key is used to look up the CustomerID in the
Customer table where the CustomerID is the primary key
Customer table SalesTransaction table
CustomerID (PRIMARY KEY) SalesID
CustomerName SalesDate
CustomerID (FOREIGN KEY) 22
23. Relationships
• Relationships establishes the association between
common fields in two tables
• Common field links two tables to each other, thus
ensuring connection between the data in the
tables within the same database
• REMEMBER: Access uses related tables - one table
can find and use data in another table
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24. What will we learn in this subject?
• Access objects – Table, Query, Form, Report,
Macro
• Switchboard (is also a form)
• SQL
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Notas del editor
U can insert an email. Collection of data. ex.:
Not all people. Present data, ex. cgpa
DBMS; ex, atm
Example:An organization had records of employees in a table (entity type) called "Employees". In the table there would be attributes/columns such as First Name, Last Name, Job Name and Wage. The company also has data about the employee’s children in a separate table called "Children" with attributes such as First Name, Last Name, and date of birth. The Employee table represents a parent segment and the Children table represents a Child segment. These two segments form a hierarchy where an employee may have many children, but each child may only have one parent.
A record may be an owner in any number of sets, and a member in any number of setsBranches can be connected to multiple nodesThe network model is able to represent redundancy in data more efficiently than in the hierarchical model
