- A
Use ALTER TABLE ADD COLUMN; Spanner applies the change online without downtime.
Correct. Spanner's DDL is online and non-blocking.
- B
Export the table, modify the schema in a temporary table, and import it back.
Why wrong: This is a legacy approach that involves significant downtime and complexity.
- C
Use CREATE INDEX to add the column as an index.
Why wrong: An index is not a column; this does not add a column to the table.
- D
Create a new table with the additional column, backfill data from the old table, then rename the tables.
Why wrong: This manual approach is unnecessary and risky. Spanner supports online ALTER TABLE.
Question 206 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 financial services company uses Cloud Spanner for a globally distributed application. They need to add a new column to an existing table that contains billions of rows. The change must not cause any downtime or performance degradation. How should the engineer implement this schema change?
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 ALTER TABLE ADD COLUMN; Spanner applies the change online without downtime.
Cloud Spanner supports online schema changes via the `ALTER TABLE ADD COLUMN` statement, which applies the change asynchronously without locking the table or causing downtime. Spanner uses a multi-phase approach to add columns, allowing reads and writes to continue uninterrupted while the schema change propagates across all nodes and regions.
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.
- ✓
Use ALTER TABLE ADD COLUMN; Spanner applies the change online without downtime.
Why this is correct
Correct. Spanner's DDL is online and non-blocking.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Export the table, modify the schema in a temporary table, and import it back.
Why it's wrong here
This is a legacy approach that involves significant downtime and complexity.
- ✗
Use CREATE INDEX to add the column as an index.
Why it's wrong here
An index is not a column; this does not add a column to the table.
- ✗
Create a new table with the additional column, backfill data from the old table, then rename the tables.
Why it's wrong here
This manual approach is unnecessary and risky. Spanner supports online ALTER TABLE.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that schema changes on large distributed databases require manual backfill or table recreation, but Spanner's online DDL handles this transparently without downtime.
Detailed technical explanation
How to think about this question
Under the hood, Spanner's schema change uses a distributed, asynchronous process that first adds the column as a metadata-only change, then gradually backfills default values in the background across all splits and replicas. This ensures that the schema change is eventually consistent without blocking ongoing transactions, and the new column is immediately available for writes with a default value if specified.
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: Use ALTER TABLE ADD COLUMN; Spanner applies the change online without downtime. — Cloud Spanner supports online schema changes via the `ALTER TABLE ADD COLUMN` statement, which applies the change asynchronously without locking the table or causing downtime. Spanner uses a multi-phase approach to add columns, allowing reads and writes to continue uninterrupted while the schema change propagates across all nodes and regions.
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.
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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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