PCDE Design and implement database schemas Practice Question
This PCDE practice question tests your understanding of design and implement database schemas. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 company is migrating a large Oracle database to Cloud Spanner. They need to define the schema for relational tables with foreign keys. Which THREE considerations are important when designing the Spanner schema? (Choose three.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use INTERLEAVE tables to model parent-child relationships.
Options A, B, and D are correct. Spanner supports interleaved tables (A) for parent-child relationships, foreign key constraints (B) for referential integrity, and secondary indexes (D) for query performance on non-key columns. Option C is false because composite primary keys are common. Option E is false because primary key columns cannot be NULL.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Use NULL values in primary key columns to allow optional fields.
Why it's wrong here
Primary key columns cannot be NULL; they must have unique non-null values.
✓
Use INTERLEAVE tables to model parent-child relationships.
Why this is correct
Interleaving allows co-locating parent and child rows, reducing read latency.
Related concept
Standard ACLs match source addresses.
✗
Avoid using composite primary keys; use single-column keys instead.
Why it's wrong here
Composite primary keys are common and recommended in Spanner for data distribution.
✓
Define secondary indexes for querying on non-key columns.
Why this is correct
Secondary indexes improve query performance on columns not part of the primary key.
Related concept
Standard ACLs match source addresses.
✓
Foreign keys are automatically enforced in Cloud Spanner.
Why this is correct
Cloud Spanner supports foreign key constraints with enforcement.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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. ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement. 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.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCDE ACL questions on filtering logic and placement.
Design and implement database schemas — This question tests Design and implement database schemas — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Use INTERLEAVE tables to model parent-child relationships. — Options A, B, and D are correct. Spanner supports interleaved tables (A) for parent-child relationships, foreign key constraints (B) for referential integrity, and secondary indexes (D) for query performance on non-key columns. Option C is false because composite primary keys are common. Option E is false because primary key columns cannot be NULL.
What should I do if I get this PCDE question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCDE ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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