Ch1 Flashcards
(15 cards)
Database
Structure that can store information about
Different categories of information , relationships between those categories
Entity
Entities for TAL distributors
EX: object , person , place event or idea
Attributes
Characteristics or property of entity
May called a field or column
Relationship
Association between entities
Form
Screen object that used to maintain , view and print data from a database .
DBMs creates form that TAL distribute needs
DBMS
program or collection of program, through which user interact with database
Data file
File used to store data , computer counterpart to ordinary paper file
ER diagram
Visual way represent database .
Rectangles represent entities .
Lines represent relationship between entities
Advantage of database processing
Getting more information from the same amount of dara
- shaing data
- contrilling redundancy
- facilitating consistency
- increasing productivity
Disadvantage of database
- Larger file size
- increased complexity
- Greater impact of failure
- more diffiuclt recovery
User view
Set of requirements necessary to support operation of a particular database user
Represent the user view as a collection of tables
Step 1 : determine the entities involved and create a separate table for each type of entity
Step 2 : determine the primery key for each table
Step 3 : determine the properties for each entity
Step 4 : determine relationship between the entities
One-to-many
Simplest implementation is to treat it as one to many relationship
One-to-many
Include primary key of the one table as a foreign key in the many table
Many _ to _ many
Create a new table whose primary key is the combination of the primary keys of the original tables
