The difficulties of Managing Data
- Data increases exponentially
- Data are scattered throughout organizations and collected by many individuals using various
methods and devices
- Data come from multiple sources: internal sources, personal sources, and external sources
- Data degrade over time
- Data are also subject to data rot.
- Data errors
- Data security, quality, and integrity are critical.
Legislation can affect data archiving requirements: PIPEDA Jan 1, 2004
A database management system (DBMS) is a set of program that provides users with tools to
add, delete, access, and analyze data stored in one location. An organization can access the data
by using query and reporting tools that are part of the DBMS or by using application program
specifically written to access the data
Advantages of Database Management system:
- Data redundancy 资料重复性 reduced
- Data independence more achievable
- Data can be effectively managed centrally- Increases data accessibility
- Security over data can be more consistent (Data inconsistency: Various copies of the data do
- Maximize Data security/Data integrity/Data independence
Disadvantages of Database Management Systems
- More complex (and costly) to set up and maintain
- Complex structures may be slower for processing high volume periodic transaction updates
Data Hierarchy - Bit/Byte=character/Field/Record/File
- A logical grouping of characters into a work, a small group of words, or an identification
number is called a field. It can also contain data other than text and numbers.
- A logical grouping of related fields, such as the student’s name, and the courses taken, the date,
and the grade, compose a record.
- A logical grouping of related records is called a file or tale.
- A logical grouping of related tables would constitute a database. Data design for database
- Data model is a diagram that represents entities in the database and their relationships
- An entity (record) is a person, place, thing, or event
- Each characteristic or quality of a particular entity (field) is called attribute is the context of
- Every record in a table must contain at least one attribute/field that uniquely identifies that
record so that it can be retrieved, updated, and sorted primary key
- Secondary keys are other fields that have some identifying information but typically do not
identify the record or entity with complete accuracy.
Designers plan and develop the database through a process called entity-relationship modeling,
using an entity-relationship diagram
- A given type are grouped in entity classes – Student, parking permit, class and professor
- An instance of an entity class is the presentation of one particular entity – Student (Lihang
Zhong, 145-89-7123) is the instance of the Student entity class.
The Relational Database Model is based on the concept of two-dimensional tables - a flat file
that contain all of the records and attributes
- Structured query languages (SQL) is the most popular uery language used to request
information Allows people to perform complicated searches by using relatively simple
statement or keywords
- Another way to find information in data base is to use query by example (QBE)
- Data Dictionary defines the format necessary to enter the data into the database
- Normalization is a method for analyzing and reducing a relational database to its most
streamlined form for minimum redundancy, maximum data integrity, and best processing