- A
Create a secondary index on (OrderDate) only
Why wrong: Cannot filter by customer efficiently.
- B
Create a secondary index on (CustomerId, OrderDate)
Why wrong: No descending order requires sorting; also lacks INCLUDE, requiring base table lookup.
- C
Use a manual table scan with filter
Why wrong: No index used; slow for large tables.
- D
Create a secondary index on (CustomerId, OrderDate DESC) with INCLUDE (OrderId, Status)
Index covers the query completely, providing efficient ordered retrieval.
Question 226 of 1,000
PCDE Design and implement database schemas Practice Question
This PCDE practice question tests your understanding of design and implement database schemas. 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.
You have a Cloud Spanner table 'Orders' with columns: OrderId, CustomerId, OrderDate, Status. You need to support a query that finds all orders for a customer in the last 30 days, sorted by OrderDate descending, with strong consistency. Using only indexes, what is the best approach?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
✓
Create a secondary index on (CustomerId, OrderDate DESC) with INCLUDE (OrderId, Status)
Option D is correct because it creates a covering index with the exact sort order needed (DESC on OrderDate) and includes all required columns (OrderId, Status) to avoid back-to-table lookups. This ensures strong consistency in Cloud Spanner by using a single index scan without needing to read the base table, while the composite key on (CustomerId, OrderDate) efficiently filters by customer and date range.
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.
- ✗
Create a secondary index on (OrderDate) only
Why it's wrong here
Cannot filter by customer efficiently.
- ✗
Create a secondary index on (CustomerId, OrderDate)
Why it's wrong here
No descending order requires sorting; also lacks INCLUDE, requiring base table lookup.
- ✗
Use a manual table scan with filter
Why it's wrong here
No index used; slow for large tables.
- ✓
Create a secondary index on (CustomerId, OrderDate DESC) with INCLUDE (OrderId, Status)
Why this is correct
Index covers the query completely, providing efficient ordered retrieval.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud Spanner requires a composite index with the correct sort order (DESC) and covering columns for optimal query performance. A simple index on OrderDate alone would not efficiently filter by CustomerId, and a table scan is not recommended when an index can satisfy the query.
Detailed technical explanation
How to think about this question
Cloud Spanner secondary indexes are stored as separate tables that are automatically maintained and strongly consistent. When you specify DESC on a column in the index definition, Spanner stores the index entries in descending order, allowing the query to read rows directly in the required sort order without an additional sort operation. The INCLUDE clause adds non-key columns to the index's storage, making it a covering index that eliminates the need to fetch data from the base table, reducing read latency and resource consumption.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCDE question test?
Design and implement database schemas — This question tests Design and implement database schemas — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a secondary index on (CustomerId, OrderDate DESC) with INCLUDE (OrderId, Status) — Option D is correct because it creates a covering index with the exact sort order needed (DESC on OrderDate) and includes all required columns (OrderId, Status) to avoid back-to-table lookups. This ensures strong consistency in Cloud Spanner by using a single index scan without needing to read the base table, while the composite key on (CustomerId, OrderDate) efficiently filters by customer and date range.
What should I do if I get this PCDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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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