Third normal form
Third normal form is a relational schema condition in which the relation is in second normal form and non-key attributes depend only on the key, not transitively on other non-key attributes.
100 SQL Server Mistakes and How to Avoid Them
Third normal form is a relational design state in which the relation is in second normal form and non-key attributes are not transitively dependent on the key.
- How it is used
- Guides relational schema design toward a practical normalization target for most cases.
- How deep it goes
- Defines 3NF through non-key dependencies and prescribes moving offending attributes into new entities.
- Examples
- Uses a sales, purchasing, products, addresses, and customer design as a normalization artifact.
- What you can do after
- Evaluate/understand whether non-key attributes should be separated into related entities.
Read how 100 SQL Server Mistakes and How to Avoid Them explains third normal form →
Grokking Relational Database Design
Third normal form is a relational design level in which the table is in second normal form and non-key attributes do not depend transitively on a key.
- How it is used
- Guides table decomposition to minimize redundancy, prevent anomalies, and strengthen data integrity.
- How deep it goes
- Defines transitive dependency, demonstrates its employee-table form, and prescribes decomposition into directly dependent tables.
- Examples
- Uses an employee table whose department details create a transitive dependency, then separates employee and department data.
- What you can do after
- Apply a 3NF checklist and split tables containing transitive dependencies into related tables.
Read how Grokking Relational Database Design explains third normal form →
Related concepts
- transitive dependencycontrasts with · A transitive dependency is a dependency reached indirectly through one or more intermediate dependencies rather than declared or connected directly.
- normalizationkind of · Normalization is the process of transforming a value, representation, or data structure to satisfy a specified standard, scale, or structural constraint.
- cyclecontrasts with · A cycle is a recurring sequence of connected elements or events that returns to an earlier point, forming a loop.
These guides are generated from the text of Manning books by Manning's knowledge graph and link to the sections they draw on. The full books are available on liveBook and at manning.com.