First Normal Form (1NF)
Context: FIT2094_MOC · a valid relation with a PK and no repeating groups · the first Normalisation step · partial dependencies listed here
Quick Revision
- 🎯 Objective: a valid relation with a PK and no repeating groups ➔ the first normalisation step.
- 📦 Core Components: unique PK ➔ atomic cells ➔ all attributes depend on all/part of the PK.
- ⚡ Key Constraint: still leaves partial and transitive dependencies — list partial dependencies here.
📝 Core
1. The 1NF Conditions
- Unique PK ➔ identified for each tuple.
- Valid relation ➔ entity integrity (no part of PK NULL), atomic cells (no repeating groups).
- Dependence ➔ all attributes functionally depend on all or part of the PK.
2. UNF → 1NF Steps
- Identify PK ➔ for the main relation.
- Remove repeating group ➔ into a new relation, bringing the original PK.
- New PK ➔ usually composite (original PK + repeating group’s identifier).
3. List Partial Dependencies
- Definition ➔ non-key depends on part of a composite key.
- Example ➔ in RESTOCK.
- Removed at ➔ 2NF.
When It Flips: if the UNF had no repeating group (ENROLMENT), 1NF creates no new relation — only a PK is added. 1NF is the valid-relation requirement (Relation Properties) plus a PK; anomalies persist until 2NF/3NF.
📊 Exam Execution Trace
Manual Execution Trace
UNF → 1NF for PART:
| Step / State | Action | Result |
|---|---|---|
| 0 (Init) | UNF PART | bracketed group |
| 1 | identify PK | part_no |
| 2 | remove repeating group | RESTOCK |
| 3 | new PK | (part_no, vendor_no, restock_date) |
⚠️ Common Mistakes
- 💡 Move the repeating group, never flatten ➔ a multivalued cell breaks atomicity; 1NF removes only repeating groups, leaving partial/transitive dependencies.
🧠 Active Recall
State the conditions for 1NF and the UNF→1NF steps.
- Hint: PK + atomic + remove repeating group.
Answer
- Short answer: Unique PK, entity integrity, atomic cells; move the repeating group to a new relation carrying the original PK.
- Why: Composite new PK ➔ usually original PK + repeating group’s identifier.
What must you list at 1NF, and why is 1NF still anomaly-prone?
- Hint: Partial dependencies remain.
Answer
- Short answer: List all partial dependencies; 1NF removes only repeating groups.
- Why: 2NF/3NF ➔ partial and transitive dependencies remain until removed later.