- A
The new column cannot be added if the table has existing data.
Why wrong: Spanner allows adding columns to tables with data.
- B
The new column must have a default value if it is defined as NOT NULL.
Adding a NOT NULL column without default requires a table lock; with a default it is online.
- C
CREATE INDEX will block writes on the table until the index is built.
Why wrong: CREATE INDEX is non-blocking in Spanner.
- D
ALTER TABLE can be executed while the database is serving traffic.
Schema changes are online and non-blocking.
- E
The DDL statements can be submitted together in a single ALTER DATABASE statement.
Multiple DDL statements can be batched in a single request.
Question 791 of 1,000
PCDOE Manage Database Solutions Practice Question
This PCDOE practice question tests your understanding of manage database solutions. 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 gaming company uses Cloud Spanner for a global leaderboard. They need to add a column to an existing table and create a secondary index on that column. The database must remain fully available during these changes. Which THREE statements are true?
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
✓
The new column must have a default value if it is defined as NOT NULL.
Option B is correct because in Cloud Spanner, when adding a NOT NULL column to an existing table, the column must have a DEFAULT value. This ensures that existing rows, which will be populated with the default value, satisfy the NOT NULL constraint without requiring a full table scan or blocking writes.
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.
- ✗
The new column cannot be added if the table has existing data.
Why it's wrong here
Spanner allows adding columns to tables with data.
- ✓
The new column must have a default value if it is defined as NOT NULL.
Why this is correct
Adding a NOT NULL column without default requires a table lock; with a default it is online.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
CREATE INDEX will block writes on the table until the index is built.
Why it's wrong here
CREATE INDEX is non-blocking in Spanner.
- ✓
ALTER TABLE can be executed while the database is serving traffic.
Why this is correct
Schema changes are online and non-blocking.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The DDL statements can be submitted together in a single ALTER DATABASE statement.
Why this is correct
Multiple DDL statements can be batched in a single request.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that schema changes in distributed databases require downtime or blocking, but Cloud Spanner's online DDL operations are designed to maintain full availability during both ALTER TABLE and CREATE INDEX.
Detailed technical explanation
How to think about this question
Cloud Spanner uses a distributed, synchronous replication architecture where DDL operations like ALTER TABLE and CREATE INDEX are applied as atomic schema changes across all nodes. The CREATE INDEX operation leverages Cloud Spanner's built-in change tracking to build the index incrementally without locking the table, allowing reads and writes to continue uninterrupted. This is in contrast to traditional databases where index creation often requires a full table lock.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
- →
Manage Database Solutions — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this PCDOE question test?
Manage Database Solutions — This question tests Manage Database Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The new column must have a default value if it is defined as NOT NULL. — Option B is correct because in Cloud Spanner, when adding a NOT NULL column to an existing table, the column must have a DEFAULT value. This ensures that existing rows, which will be populated with the default value, satisfy the NOT NULL constraint without requiring a full table scan or blocking writes.
What should I do if I get this PCDOE 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.
About these practice questions
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Last reviewed: Jul 4, 2026
This PCDOE 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 PCDOE exam.
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