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ENTITY RELATIONSHIP DIAGRAM
Primary key
Relationships among entities
1:1
1:M
M:M
Draw the entities and their relationships accurately.
Introduction
The database environment and development process
Database: organized collection of logically related data
Data: stored representation of meaningful objects and events
Structured: numbers, text, dates
Unstructured: images, videos, documents
Information: data processed to increase knowledge in the person using the data.
Metadata: data that describes the properties and context of user data
A data in context: which helps users understand data
Summarized data: graphical displays turn data into useful info. That managers can use for
decision making and interpretation
Disadvantages of file processing
Program data dependence
Duplication of data
Limited data sharing
Lengthy development times
Excessive program maintenance
Problems with data dependency
Each Application programmer must maintain his own data
Each ap needs to include code for the metadata of each file
Each ap must have its own processing routines for reading, inserting, updating and deleting
data
Lack of coordination and central control
Non-standard file formats
Duplicate data
Diagrammatic representation shown
Problems with data redundancy
Waste of space to have duplicate data
Causes more maintenance headaches
The biggest problem:
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