DA0-002 Data Concepts and Environments Practice Question
Which TWO of the following are benefits of database normalization to 3NF? (Select 2)
⚠ Common exam trap
It's easy for candidates to confuse normalization with denormalization, assuming that reducing redundancy always improves query performance, when in fact normalization often increases join complexity and can slow down read queries.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Reduces data redundancy
Normalization to 3NF eliminates transitive dependencies, which directly reduces data redundancy by ensuring each non-key attribute depends only on the primary key. This reduction in redundancy also increases data integrity because updates, inserts, and deletes are less likely to create inconsistencies or anomalies. In a relational database, 3NF achieves this without sacrificing the ability to reconstruct the original data via joins.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Improves query performance for all queries
Why it's wrong here
Normalisation splits data across more tables, so most read queries need additional joins, which typically increases I/O and CPU cost rather than improving it. It is tempting because normalisation does reduce redundancy and update anomalies, and it can help specific write-heavy or insert workloads, but it does not speed up every query.
- ✓
Reduces data redundancy
Why this is correct
Third normal form eliminates repeating groups and transitive dependencies, so each fact is stored once in its owning table. This satisfies the redundancy benefit by removing duplicate copies that would otherwise need synchronising across the schema.
- ✗
Simplifies complex joins
Why it's wrong here
Normalisation to 3NF splits data into many narrow tables, so queries typically require additional joins rather than fewer. It is tempting because denormalisation, the opposite process, deliberately merges tables to reduce join complexity for read-heavy reporting workloads. Here, 3NF's actual benefits are eliminating transitive dependencies and reducing update anomalies, not simplifying joins.
- ✗
Eliminates all data anomalies
Why it's wrong here
Third normal form removes transitive dependencies and most update anomalies, but cannot eliminate all of them; anomalies from other causes, such as missing keys or unenforced constraints, remain. It is tempting because anomaly reduction is genuinely a headline benefit of normalisation, just not an absolute guarantee.
- ✓
Increases data integrity
Why this is correct
Because each fact lives in exactly one place under 3NF, inserts, updates and deletes cannot leave contradictory values scattered across tables. This satisfies the integrity benefit by preventing update anomalies that arise from duplicated, partially maintained data.
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