2017-04-05.12-31-29png TESTING YOUR UNDERSTANDING Exercise 7-1 Figure 7-25 shows
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2017-04-05.12-31-29png TESTING YOUR UNDERSTANDING Exercise 7-1 Figure 7-25 shows an initial data model for a small ibrary.It is incomplete, so as you answer the questions below consider what else might need to be included. a Explain to the librarian what the initial data model means. b) Design tables for database which would capture the information represented by the model, Include primary and foreign keys and other appropriate constraints Title cat num belongs to title author m 11 Person tem ast name rst name Om copy num purchase date Figure 7-25. Draft data model for a small libraryExplanation / Answer
1. Initial Data Model
A Data Model is for converting a complex system into a simpler system by means of a diagrammatic representation.
The initial data model is a template or a blueprint of the proposed system.This will carry only the skeleton of the system and the details will not be used.
This involves the collection of data,relationships between the data, data semantics and constraints.
The initial data model of a library will have
b) Tables
Table Name: Books
Field Name
Data type
Description
Cat_num (FK)
Integer
Not Null
Title
Varchar(40)
Not Null
Author_name
Varchar(30)
Not Null
Edition
Varchar(40)
Not Null
Availability
Bool
Not Null
Relationships:
Book_Title(Parent) Category by category number (Child)
Cardinality = One to many
Table Name: Category
Table : Person/Borrower
Relationships
Person to Books Cradinality N -1
Table Name: Items
Relationships
Person to Item Cardinality 0-N /1-N
Book to Item Cardinality 1...1-n
Field Name
Data type
Description
Book_id (PK) Integer Not NullCat_num (FK)
Integer
Not Null
Title
Varchar(40)
Not Null
Author_name
Varchar(30)
Not Null
Edition
Varchar(40)
Not Null
Availability
Bool
Not Null
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