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Bite sized training sessions: Data Modelling – Part 2 of 2 Data Definitions. Objectives. To understand What is a data model … and what it is not! Why do data modelling To be able to Read a data model Build a data model Critically review a data model. What is a data model?.
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What is a data model … and what it is not!
Why do data modelling
To be able to
Read a data model
Build a data model
Critically review a data model
Specification of the data that is required in order for
The solution to meet it’s objectives
Processes to be able to run
A data model comprises:
A diagram showing the requireddata dependencies
A set of data definitions required foreach attribute on the diagram
Also referred to as:
Logical Data Model (LDM)
Entity Relationship Diagram (ERD)
A physical design for storing data
A database design
Database table definitions
Entity A real world thing or an interaction between 2 or more real world things.
Relationship How and why entities depend on each other (the relationship) and what that relationship is (the cardinality of the relationship).
Attribute The atomic pieces of information that we need to know about entities.
“The atomic pieces of information that we need to know about entities”
E.g. On a Customer entity “1st child name”, “2nd child name”…
E.g. On Customer entity “order date”
The following should have been addressed via entity relationship diagram:
must be between 09:00 and 17:30 and
always display as YYYY-MM-DD:HH.MM
I own a florist’s shop called My Florist.
I want to start emailing reminders to customers when special occasions are due for which they have brought flowers in the past – for example a spouse’s birthday.
We have already got a data model of the requirements so lets define the data for Customer.
(3 years, 302 working days per year, 15 customers per day)
Someone who purchases flowers from My Florist
The customer has purchased flowers from My Florist for a Special Occasion in the past, so reminders need to be sent just before the anniversary of the event.
The email address given by the customer at the point of sale of flowers for a Special Occasion