GCP-ADP Data Analysis And Presentation Practice Question
You need to perform a time-series analysis in BigQuery. Your data contains timestamps at a millisecond level, but you need to aggregate by hour. What is the most performant way to truncate the timestamp?
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
✓
TIMESTAMP_TRUNC(timestamp_column, HOUR).
The TIMESTAMP_TRUNC function is highly optimized for this specific task in BigQuery.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
EXTRACT(HOUR FROM timestamp_column).
Why it's wrong here
This just returns the hour (0-23) and loses the date information.
- ✗
CAST(timestamp_column AS STRING).
Why it's wrong here
Casting to string is extremely slow and makes grouping difficult.
- ✓
TIMESTAMP_TRUNC(timestamp_column, HOUR).
Why this is correct
This function is the standard and most performant way to truncate timestamps.
- ✗
Using a CASE statement to manually subtract milliseconds.
Why it's wrong here
Manual arithmetic on timestamps is prone to errors and is not performant.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Google Cloud exam blueprint
This GCP-ADP 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 GCP-ADP exam.