- A
Add the new columns using ALTER TABLE ADD COLUMN.
Why wrong: Adding columns is possible but not sufficient; you also need to change the existing column's mode. However, the question asks for three steps; D is a step but not included as one of the three required ones because it's trivial. Actually, the correct three steps are A, B, C. D is not required because you can add columns in the new table definition. So D is not needed.
- B
Use the ALTER TABLE SET OPTIONS statement to change the column mode to NULLABLE.
ALTER TABLE ... ALTER COLUMN SET DATA TYPE or SET OPTIONS can change mode to NULLABLE.
- C
Update the IAM permissions on the table.
Why wrong: IAM permissions are unrelated to schema changes.
- D
Use CREATE OR REPLACE TABLE with the new schema and import data.
Recreating the table with the new schema is a reliable way to apply schema changes.
- E
Export the table to Cloud Storage in Avro format.
Exporting data ensures no loss during schema change; Avro supports nulls.
PDE Maintaining and Automating Data Workloads Practice Question
This PDE practice question tests your understanding of maintaining and automating data workloads. 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 BigQuery table with a REQUIRED column that you now need to allow NULL values. You also need to add two new nullable columns. Which THREE steps are required to achieve this schema evolution? (Choose 3)
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 the ALTER TABLE SET OPTIONS statement to change the column mode to NULLABLE.
BigQuery requires exporting data, modifying the schema, and importing data or using SQL statements. The schema can be updated via `bq update` or ALTER TABLE. Simply adding columns is possible, but changing from REQUIRED to NULLABLE requires recreation or ALTER TABLE CHANGE COLUMN.
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.
- ✗
Add the new columns using ALTER TABLE ADD COLUMN.
Why it's wrong here
Adding columns is possible but not sufficient; you also need to change the existing column's mode. However, the question asks for three steps; D is a step but not included as one of the three required ones because it's trivial. Actually, the correct three steps are A, B, C. D is not required because you can add columns in the new table definition. So D is not needed.
- ✓
Use the ALTER TABLE SET OPTIONS statement to change the column mode to NULLABLE.
Why this is correct
ALTER TABLE ... ALTER COLUMN SET DATA TYPE or SET OPTIONS can change mode to NULLABLE.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Update the IAM permissions on the table.
Why it's wrong here
IAM permissions are unrelated to schema changes.
- ✓
Use CREATE OR REPLACE TABLE with the new schema and import data.
Why this is correct
Recreating the table with the new schema is a reliable way to apply schema changes.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Export the table to Cloud Storage in Avro format.
Why this is correct
Exporting data ensures no loss during schema change; Avro supports nulls.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
Identify which PDE 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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Maintaining and Automating Data Workloads — study guide chapter
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FAQ
Questions learners often ask
What does this PDE question test?
Maintaining and Automating Data Workloads — This question tests Maintaining and Automating Data Workloads — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use the ALTER TABLE SET OPTIONS statement to change the column mode to NULLABLE. — BigQuery requires exporting data, modifying the schema, and importing data or using SQL statements. The schema can be updated via `bq update` or ALTER TABLE. Simply adding columns is possible, but changing from REQUIRED to NULLABLE requires recreation or ALTER TABLE CHANGE COLUMN.
What should I do if I get this PDE question wrong?
Identify which PDE 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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jul 4, 2026
This PDE 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 PDE exam.
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