- A
Store all data in a flat table with repeated order info per line item
Why wrong: This leads to data duplication and larger storage, but nested fields are more efficient.
- B
Use nested and repeated fields (orders table with line items as REPEATED RECORD)
Nested/repeated fields allow storing order with line items in one row, eliminating joins.
- C
Normalize into separate orders and line_items tables, join on order_id
Why wrong: Joins are expensive in BigQuery; denormalized is preferred for performance.
- D
Use a partitioned table on order date
Why wrong: Partitioning is a storage optimization, not a schema design for relationships.
Question 467 of 1,000
PDE Storing the Data Practice Question
This PDE practice question tests your understanding of storing the data. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A data engineer needs to design a schema in BigQuery for a dataset that contains customer orders. Each order has a header and multiple line items. Queries frequently need to retrieve the entire order including line items. Which schema design is MOST performant and cost-effective?
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
✓
Use nested and repeated fields (orders table with line items as REPEATED RECORD)
Option B is correct because BigQuery is optimized for denormalized schemas using nested and repeated fields (REPEATED RECORD). Storing line items as a repeated record within the orders table avoids expensive JOIN operations, reduces data shuffling, and allows BigQuery to scan only the necessary columns, making queries that retrieve entire orders with line items both faster and more cost-effective.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Store all data in a flat table with repeated order info per line item
Why it's wrong here
This leads to data duplication and larger storage, but nested fields are more efficient.
- ✓
Use nested and repeated fields (orders table with line items as REPEATED RECORD)
Why this is correct
Nested/repeated fields allow storing order with line items in one row, eliminating joins.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Normalize into separate orders and line_items tables, join on order_id
Why it's wrong here
Joins are expensive in BigQuery; denormalized is preferred for performance.
- ✗
Use a partitioned table on order date
Why it's wrong here
Partitioning is a storage optimization, not a schema design for relationships.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google often tests the misconception that normalization (Option C) is always the best practice for relational databases, but in BigQuery's distributed, columnar architecture, denormalization with nested and repeated fields is the recommended pattern for performance and cost efficiency.
Detailed technical explanation
How to think about this question
BigQuery stores nested and repeated fields as a columnar format using Protocol Buffers (protobuf), allowing repeated records to be stored as arrays within a single row. This eliminates the need for JOINs because all line items are co-located with their order header, and queries can unnest the array using the UNNEST function, which is highly optimized for columnar scanning and avoids cross-row shuffling. In real-world scenarios, this design can reduce query costs by over 50% compared to normalized schemas when retrieving full orders.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this PDE question test?
Storing the Data — This question tests Storing the Data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use nested and repeated fields (orders table with line items as REPEATED RECORD) — Option B is correct because BigQuery is optimized for denormalized schemas using nested and repeated fields (REPEATED RECORD). Storing line items as a repeated record within the orders table avoids expensive JOIN operations, reduces data shuffling, and allows BigQuery to scan only the necessary columns, making queries that retrieve entire orders with line items both faster and more cost-effective.
What should I do if I get this PDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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