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PCDE Designing a data warehouse for BI Practice Question
A company is designing a data warehouse for BI. They need to support both detailed transaction analysis and high-level aggregated reports. Which schema design best balances storage and query performance?
⚠ Common exam trap
Google Cloud often tests the misconception that snowflake schemas are always better for storage efficiency, but the trap here is that the question explicitly balances storage and query performance, and the star schema provides the best trade-off by avoiding excessive joins while keeping dimensions manageable.
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
✓
Star schema with fact and dimension tables
The star schema is the optimal design for balancing storage and query performance in a BI data warehouse because it separates transactional data into fact tables (for detailed analysis) and dimension tables (for context), enabling fast aggregations via star joins while avoiding the storage overhead of full denormalization. This structure directly supports both granular transaction queries and high-level rollups without the complexity or performance penalty of snowflake schemas or the redundancy of fully denormalized tables.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Fully denormalized single table
Why it's wrong here
Denormalized tables cause data redundancy and slower updates.
- ✗
Wide column store with no schema
Why it's wrong here
No schema is unsuitable for structured BI reporting.
- ✓
Star schema with fact and dimension tables
Why this is correct
Star schema is standard for BI, enabling fast aggregations and easy reporting.
- ✗
Snowflake schema with normalized dimensions
Why it's wrong here
Snowflake reduces redundancy but increases join complexity, slowing queries.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This PCDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCDE exam.