DBMS
ER Design Project: E-commerce System
An e-commerce database covering customers, products, carts, orders and payments, including why an order line must copy the price it was sold at rather...
#ER Model
Entity relationship modelling.
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DBMS
ER Design Project: Library System
A library database that separates a title from a physical copy, models issue and return correctly, and shows why the obvious single book table quietly...
DBMS
ER Design Project: Banking System
A banking database with a generalisation hierarchy for account types, a many to many customer to account relationship, and a transaction model that ne...
DBMS
ER Design Project: Hospital Database
A hospital database designed end to end, including a weak entity for prescription lines, a ternary relationship for treatment, and the privacy decisio...
DBMS
ER Design Project: College Database
A complete college database designed from a written requirement: entities, attributes, relationships, cardinality, participation, the ER diagram and t...
DBMS
Converting an ER Diagram into Relational Tables
Seven rules turn any ER diagram into a relational schema: entities become tables, one to many puts a foreign key on the many side, many to many become...
DBMS
Extended ER: Generalisation, Specialisation and Aggregation
The extended ER model adds inheritance to ER. Specialisation splits an entity into subclasses, generalisation combines subclasses into a superclass, a...
DBMS
Drawing and Reading ER Diagrams
A complete guide to ER notation and a repeatable eight step method for turning a written requirement into a correct, readable ER diagram.
DBMS
Strong and Weak Entities
A weak entity has no key of its own and can only be identified through an owner entity. It is drawn with a double rectangle, joined by an identifying...
DBMS
Cardinality and Participation Constraints
Cardinality says how many entities on one side may relate to entities on the other; participation says whether every entity must take part. Together t...
DBMS
Relationships, Relationship Sets and Degree
A relationship is an association among entities. Relationship types have a degree, may carry their own attributes, and may connect an entity type to i...
DBMS
Keys in the ER Model
A key attribute distinguishes one entity from another. Understanding super keys, candidate keys, primary keys and partial keys at design time prevents...