- A
Take the application offline, run ALTER TABLE to add the column, then bring the application back online
Why wrong: Unnecessary downtime; Spanner supports online schema changes.
- B
Create a new table with the column, copy data using Dataflow, then rename the tables
Why wrong: This is overly complex and involves downtime during the rename; Spanner supports direct online schema changes.
- C
Add the column without a default, then run a batch update to set the default value
Why wrong: This approach requires a separate batch operation that may cause performance impact, while Spanner allows online addition with default.
- D
Use ALTER TABLE ADD COLUMN with DEFAULT 0; the operation is online and non-blocking
Spanner schema changes are non-blocking; adding a column with a default is immediate and does not cause downtime.
PCDOE Design and Plan Database Solutions Practice Question
This PCDOE practice question tests your understanding of design and plan 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 company is using Cloud Spanner and needs to add a new column to an existing table that has billions of rows. The column must have a default value of 0. The team is concerned about downtime. Which approach should they take to add the column with zero downtime?
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 with DEFAULT 0; the operation is online and non-blocking
Cloud Spanner supports online schema changes that are non-blocking. Adding a column with a DEFAULT value is an online operation that does not block reads or writes, and does not require copying data. The new column is added with the default value for existing rows at read time, not by backfilling.
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.
- ✗
Take the application offline, run ALTER TABLE to add the column, then bring the application back online
Why it's wrong here
Unnecessary downtime; Spanner supports online schema changes.
- ✗
Create a new table with the column, copy data using Dataflow, then rename the tables
Why it's wrong here
This is overly complex and involves downtime during the rename; Spanner supports direct online schema changes.
- ✗
Add the column without a default, then run a batch update to set the default value
Why it's wrong here
This approach requires a separate batch operation that may cause performance impact, while Spanner allows online addition with default.
- ✓
Use ALTER TABLE ADD COLUMN with DEFAULT 0; the operation is online and non-blocking
Why this is correct
Spanner schema changes are non-blocking; adding a column with a default is immediate and does not cause downtime.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- 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 PCDOE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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FAQ
Questions learners often ask
What does this PCDOE question test?
Design and Plan Database Solutions — This question tests Design and Plan 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 with DEFAULT 0; the operation is online and non-blocking — Cloud Spanner supports online schema changes that are non-blocking. Adding a column with a DEFAULT value is an online operation that does not block reads or writes, and does not require copying data. The new column is added with the default value for existing rows at read time, not by backfilling.
What should I do if I get this PCDOE question wrong?
Identify which PCDOE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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