DBMS
First Normal Form
A relation is in 1NF when every value is atomic and there are no repeating groups. It is the entry requirement for the relational model itself, not me...
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Suitable for beginners.
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DBMS
Why Normalisation Exists: Anomalies and Redundancy
Redundancy causes three anomalies: you cannot insert a fact without an unrelated one, an update must change many rows, and a delete destroys informati...
DBMS
Relation Schema and Relation Instance
A relation schema is the fixed definition of a relation; a relation instance is the set of tuples in it right now. A relational database schema is the...
DBMS
Relations, Tuples, Attributes and Domains
The relational model has exactly four structural terms. A relation is a set of tuples, a tuple is one fact, an attribute is a named column and a domai...
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: College Database
A complete college database designed from a written requirement: entities, attributes, relationships, cardinality, participation, the ER diagram and t...
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
Types of Attributes in the ER Model
Attributes are simple or composite, single valued or multivalued, stored or derived, and may be complex, key or null valued. Each type converts into t...
DBMS
Entities, Entity Sets and Entity Types
An entity is a distinguishable thing the database stores facts about, an entity type is its definition, and an entity set is the collection of entitie...
DBMS
The Relational Model as a Data Model
The relational model stores everything in tables and connects them by matching values rather than pointers. That one decision delivers declarative que...
DBMS
What a Data Model Is
A data model is the set of concepts used to describe data, relationships, semantics and constraints. Models are grouped as high level, representationa...
DBMS
One Tier, Two Tier and Three Tier Architecture
Tier architecture describes how many machines or layers a database request passes through. One tier is local, two tier puts the application on the cli...