Quick Answer
The answer is TIMESTAMP. When you apply DATE_TRUNC to a TIMESTAMP column in BigQuery, the function returns a TIMESTAMP data type, not a DATE or DATETIME, because the function preserves the input type while truncating the value to the specified granularity. For example, DATE_TRUNC(order_date, MONTH) takes a TIMESTAMP like ‘2025-03-15 14:30:00 UTC’ and returns ‘2025-03-01 00:00:00 UTC’, still as a TIMESTAMP. On the Google Professional Cloud Database Engineer exam, this is a common trap: many candidates mistakenly assume DATE_TRUNC always outputs a DATE, but the key rule is that the output data type matches the input data type. The exam tests your understanding of BigQuery’s type system and function behavior under the hood. A reliable memory tip: “Truncate the time, keep the type”—the function only chops off finer time units, never changes the column’s fundamental data type.
This PCDE practice question tests your understanding of define data structures and implement sql for business intelligence. 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.
Refer to the exhibit. The query used DATE_TRUNC(order_date, MONTH) as month. order_date is a TIMESTAMP column. What is the data type of the month column in the result?
STRING
Why wrong: The output is not a string; it is a TIMESTAMP with a time part.
DATE
Why wrong: If the input were DATE, the output would be DATE, but the exhibit shows time component, so it is TIMESTAMP.
DATETIME
Why wrong: DATE_TRUNC of a TIMESTAMP returns TIMESTAMP, not DATETIME. DATETIME has no timezone; TIMESTAMP is timezone-aware.
TIMESTAMP
DATE_TRUNC of a TIMESTAMP returns a TIMESTAMP with time set to 00:00:00.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
TIMESTAMP
In BigQuery (the SQL engine for the PCDE exam), DATE_TRUNC with a TIMESTAMP input and MONTH granularity returns a TIMESTAMP value, not a DATE or DATETIME. The function truncates the timestamp to the first day of the month at 00:00:00 UTC, preserving the TIMESTAMP data type. Therefore, the month column in the result is of type TIMESTAMP.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
STRING
Why it's wrong here
The output is not a string; it is a TIMESTAMP with a time part.
DATE
Why it's wrong here
If the input were DATE, the output would be DATE, but the exhibit shows time component, so it is TIMESTAMP.
DATETIME
Why it's wrong here
DATE_TRUNC of a TIMESTAMP returns TIMESTAMP, not DATETIME. DATETIME has no timezone; TIMESTAMP is timezone-aware.
TIMESTAMP
Why this is correct
DATE_TRUNC of a TIMESTAMP returns a TIMESTAMP with time set to 00:00:00.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often assume DATE_TRUNC returns a DATE because of the word 'DATE' in the function name, but in BigQuery the output type matches the input type, so a TIMESTAMP input yields a TIMESTAMP output.
Trap categories for this question
Command / output trap
The output is not a string; it is a TIMESTAMP with a time part.
Detailed technical explanation
Under the hood, DATE_TRUNC in BigQuery operates by zeroing out the finer granularity fields (days, hours, minutes, seconds) of the TIMESTAMP while keeping the month and year, and the result remains a TIMESTAMP with a UTC timezone offset. This matters in real-world scenarios where you need to group events by month while maintaining timezone-aware joins or comparisons with other TIMESTAMP columns. A subtle behavior: if the input TIMESTAMP has a non-UTC timezone, the truncation is applied after converting to UTC, which can shift the date boundary.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
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..
The correct answer is: TIMESTAMP — In BigQuery (the SQL engine for the PCDE exam), DATE_TRUNC with a TIMESTAMP input and MONTH granularity returns a TIMESTAMP value, not a DATE or DATETIME. The function truncates the timestamp to the first day of the month at 00:00:00 UTC, preserving the TIMESTAMP data type. Therefore, the month column in the result is of type TIMESTAMP.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
This PCDE 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 PCDE exam.
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