- A
WHERE timestamp_col BETWEEN TIMESTAMP('2023-01-01') AND TIMESTAMP('2023-01-31')
Correct. Directly referencing timestamp_col with TIMESTAMP literals enables partition pruning.
- B
WHERE TIMESTAMP_TRUNC(timestamp_col, DAY) BETWEEN '2023-01-01' AND '2023-01-31'
Why wrong: Incorrect. TIMESTAMP_TRUNC wraps the column in a function, preventing partition pruning.
- C
WHERE timestamp_col >= '2023-01-01' AND timestamp_col < '2023-02-01'
Correct. Directly referencing timestamp_col with string literals also enables partition pruning because BigQuery implicitly converts the strings to TIMESTAMP.
- D
WHERE DATE(timestamp_col) BETWEEN '2023-01-01' AND '2023-01-31'
Why wrong: Incorrect. DATE wraps the column in a function, preventing partition pruning.
Question 701 of 1,000
Define data structures and implement SQL for Business Intelligence →hardMultiple ChoiceObjective-mapped
BigQuery Partition Pruning with TIMESTAMP — Correct WHERE Clause for Performance
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.
A company has a BigQuery table with a TIMESTAMP column and wants to query data for a specific date range efficiently. Which WHERE clause ensures partition pruning if the table is partitioned by that TIMESTAMP column?
Quick Answer
The answer is the WHERE clause using BETWEEN with TIMESTAMP functions, as in WHERE timestamp_col BETWEEN TIMESTAMP('2023-01-01') AND TIMESTAMP('2023-01-31'). This is correct because BigQuery partition pruning on a TIMESTAMP-partitioned table requires the filter to reference the raw column without any wrapping function—such as DATE(timestamp_col) or CAST—so the query engine can directly compare partition boundaries against the literal TIMESTAMP values and scan only the relevant partitions. On the Google Professional Cloud Database Engineer exam, this tests your understanding of how partition elimination works with temporal columns; a common trap is applying a date function to the column, which disables pruning and forces a full table scan. The memory tip is “no function on the partition column”—keep the column bare and use TIMESTAMP() for the literals to guarantee pruning.
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
✓
WHERE timestamp_col BETWEEN TIMESTAMP('2023-01-01') AND TIMESTAMP('2023-01-31')
Both options A and C directly reference the partition column (timestamp_col) without wrapping it in a function, which allows BigQuery to perform partition pruning. Option A uses explicit TIMESTAMP literals, and Option C uses string literals that are implicitly cast to TIMESTAMP; both are valid for pruning. Options B and D apply functions (TIMESTAMP_TRUNC, DATE) to the column, which disable partition pruning.
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.
- ✓
WHERE timestamp_col BETWEEN TIMESTAMP('2023-01-01') AND TIMESTAMP('2023-01-31')
Why this is correct
Correct. Directly referencing timestamp_col with TIMESTAMP literals enables partition pruning.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
WHERE TIMESTAMP_TRUNC(timestamp_col, DAY) BETWEEN '2023-01-01' AND '2023-01-31'
Why it's wrong here
Incorrect. TIMESTAMP_TRUNC wraps the column in a function, preventing partition pruning.
- ✓
WHERE timestamp_col >= '2023-01-01' AND timestamp_col < '2023-02-01'
Why this is correct
Correct. Directly referencing timestamp_col with string literals also enables partition pruning because BigQuery implicitly converts the strings to TIMESTAMP.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
WHERE DATE(timestamp_col) BETWEEN '2023-01-01' AND '2023-01-31'
Why it's wrong here
Incorrect. DATE wraps the column in a function, preventing partition pruning.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the misconception that any filter on a partitioned column will trigger pruning, but the trap here is that wrapping the partition column in a function (like DATE, TIMESTAMP_TRUNC, or implicit casts) disables pruning, so only a bare column reference with compatible literal types guarantees efficient partition elimination.
Detailed technical explanation
How to think about this question
BigQuery's partition pruning works by comparing the partition column's values directly against literal expressions in the WHERE clause; any function or type cast on the column breaks the predicate pushdown to the storage layer. For ingestion-time partitioned tables, the pseudo-column _PARTITIONTIME behaves similarly, but for column-based partitioning, the column must appear bare in the filter. In practice, using a string literal for a TIMESTAMP column (as in option C) may succeed in some contexts but is unreliable and can silently scan all partitions if the column type is not implicitly castable.
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 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
Questions learners often ask
What does this PCDE question test?
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: WHERE timestamp_col BETWEEN TIMESTAMP('2023-01-01') AND TIMESTAMP('2023-01-31') — Both options A and C directly reference the partition column (timestamp_col) without wrapping it in a function, which allows BigQuery to perform partition pruning. Option A uses explicit TIMESTAMP literals, and Option C uses string literals that are implicitly cast to TIMESTAMP; both are valid for pruning. Options B and D apply functions (TIMESTAMP_TRUNC, DATE) to the column, which disable partition pruning.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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