What is normalization
method to control redundancy in data stored and used
Ensures information quality and prevents errors and inconsistencies
Progressive decomposition of data sets into smaller, structured entities (tables). Well organised entities should respect at least 3NF
What is 1NF how do you choose it
- Entity must have at least one key
- All attributes must be atomic (single values only).
What is a key
one or more attributes that uniquely identity each row
Value is mandatory and must be unique
How to choose primary key
Shortest, stable, controlled
What does atomic mean
only one value per attribute in each record
What is 2NF
- Must be already in 1NF
- Every non-key attribute depends on the entire key not just part of it
What is 3NF
- Already in 2NF
- All non-key attributes depend directly on the key, no other attribute
What is the conceptual model and its attributes
identifies and organizes data an org. needs to function
structures data into entities
Each entity includes attributes
Associations (lines) show the relationship between entities
The blue verb explains relationship direction
Cardinalities (symbols) show how many instances of one entity can be linked to instances of another
What is the logical model
Bridge between normalization and conceptual model
Shows relationship between entities using keys
What is the foreign key
ensures consistency by pointing to a valid PK in another table
Logical model vs Conceptual model
The conceptual data model is the business view: it names the main things (entities) and how they relate, in plain language, with cardinalities/rules—no tables or keys yet. Ex.: Customer —places→ Order —contains→ Product.
The logical data model turns that into an implementable structure: entities become tables, relationships become FKs, M:N are resolved with join tables, and attributes + keys are specified.
