PCDE Practice Question: Define data structures and implement SQL for Business Intelligence
This PCDE practice question tests your understanding of define data structures and implement sql for business intelligence. 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.
Exhibit
Refer to the exhibit.
```
connection: my_bigquery_connection
dialect: bigquery_standard_sql
database: myproject
service_account_email: looker-sa@myproject.iam.gserviceaccount.com
projects:
- myproject
```
Error log: "Failed to connect to BigQuery: Access Denied: Dataset myproject:mydataset is not accessible via this connection."
A Looker developer configured a new connection to BigQuery as shown. The connection test fails with the error above. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
```
connection: my_bigquery_connection
dialect: bigquery_standard_sql
database: myproject
service_account_email: looker-sa@myproject.iam.gserviceaccount.com
projects:
- myproject
```
Error log: "Failed to connect to BigQuery: Access Denied: Dataset myproject:mydataset is not accessible via this connection."
A
The dataset mydataset does not exist in the project
Why wrong: If the dataset didn't exist, the error would be 'Not found', not 'Access Denied'.
B
The BigQuery query quota has been exceeded for the project
Why wrong: The error is about access, not quota exhaustion.
C
The Looker instance is located in a different region than the BigQuery dataset
Why wrong: Region mismatch does not cause access denied; it may cause latency but not permissions errors.
D
The Looker service account lacks the required BigQuery roles on the dataset
The error 'Access Denied' indicates missing IAM permissions for the service account.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Looker service account lacks the required BigQuery roles on the dataset
Option D is correct because the error indicates a permissions issue during the connection test. Looker uses a service account to authenticate to BigQuery, and if that service account lacks the required BigQuery roles (e.g., BigQuery Data Viewer, BigQuery Job User) on the dataset, the connection test will fail with an access denied error. The error message shown in the question (not provided here but implied) typically states 'Access Denied' or 'Permission denied' when the service account does not have the necessary IAM permissions on the dataset or project.
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 dataset mydataset does not exist in the project
Why it's wrong here
If the dataset didn't exist, the error would be 'Not found', not 'Access Denied'.
✗
The BigQuery query quota has been exceeded for the project
Why it's wrong here
The error is about access, not quota exhaustion.
✗
The Looker instance is located in a different region than the BigQuery dataset
Why it's wrong here
Region mismatch does not cause access denied; it may cause latency but not permissions errors.
✓
The Looker service account lacks the required BigQuery roles on the dataset
Why this is correct
The error 'Access Denied' indicates missing IAM permissions for the service account.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that region mismatch causes connection failures, but BigQuery datasets are global and region does not affect authentication; the real issue is almost always IAM permissions on the service account.
Detailed technical explanation
How to think about this question
Under the hood, Looker's BigQuery connection uses a service account JSON key to authenticate via OAuth 2.0. The service account must be granted IAM roles at the project or dataset level, such as 'roles/bigquery.dataViewer' for reading tables and 'roles/bigquery.jobUser' for running queries. A common subtlety is that the service account also needs the 'bigquery.datasets.get' permission to list datasets, which is included in the 'roles/bigquery.metadataViewer' role. In real-world scenarios, organizations often grant the service account only the minimal roles required, and missing any one of these can cause the connection test to fail.
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 company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
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.
Define data structures and implement SQL for Business Intelligence — This question tests Define data structures and implement SQL for Business Intelligence — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Looker service account lacks the required BigQuery roles on the dataset — Option D is correct because the error indicates a permissions issue during the connection test. Looker uses a service account to authenticate to BigQuery, and if that service account lacks the required BigQuery roles (e.g., BigQuery Data Viewer, BigQuery Job User) on the dataset, the connection test will fail with an access denied error. The error message shown in the question (not provided here but implied) typically states 'Access Denied' or 'Permission denied' when the service account does not have the necessary IAM permissions on the dataset or project.
What should I do if I get this PCDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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