- A
UNBOUNDED PRECEDING
Why wrong: `UNBOUNDED PRECEDING` defines a window from the start of the partition to the current row, not a rolling 30-day window.
- B
RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW
Correct. `RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW` creates a logical window of exactly 30 days, adjusting for gaps or multiple rows per day.
- C
PARTITION BY month
Why wrong: `PARTITION BY month` divides the result set into monthly partitions but does not define a rolling window within each partition.
- D
ROWS BETWEEN 29 PRECEDING AND CURRENT ROW
Why wrong: Incorrect. `ROWS BETWEEN 29 PRECEDING AND CURRENT ROW` only works if each day has exactly one row; if data is sparse, the time span will exceed or fall short of 30 days.
Question 285 of 1,000
Define data structures and implement SQL for Business Intelligence →mediumMultiple ChoiceObjective-mapped
PCDE Window Frame Clauses Practice Question
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. A key principle to apply: window Frame Clauses. 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 data analyst needs to create a rolling 30-day average of daily revenue. Which window function clause is required?
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
✓
RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW
Option B is correct because `RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW` ensures that the window frame includes all rows within the past 30 days, regardless of whether there is exactly one row per day. This is the proper approach for a rolling 30-day average when data may have gaps. Option D (`ROWS BETWEEN 29 PRECEDING AND CURRENT ROW`) assumes a fixed number of rows (30 rows), which only works if each day has exactly one row; if days are missing, the time window will be incorrect.
Key principle: Window Frame Clauses
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
UNBOUNDED PRECEDING
Why it's wrong here
`UNBOUNDED PRECEDING` defines a window from the start of the partition to the current row, not a rolling 30-day window.
- ✓
RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW
Why this is correct
Correct. `RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW` creates a logical window of exactly 30 days, adjusting for gaps or multiple rows per day.
Related concept
Window Frame Clauses
- ✗
PARTITION BY month
Why it's wrong here
`PARTITION BY month` divides the result set into monthly partitions but does not define a rolling window within each partition.
- ✗
ROWS BETWEEN 29 PRECEDING AND CURRENT ROW
Why it's wrong here
Incorrect. `ROWS BETWEEN 29 PRECEDING AND CURRENT ROW` only works if each day has exactly one row; if data is sparse, the time span will exceed or fall short of 30 days.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The key distinction is between `RANGE` (logical, based on date intervals) and `ROWS` (physical, based on number of rows). For a rolling 30-day average, `RANGE` with an interval correctly handles missing days, while `ROWS` fails if data is not perfectly daily.
Detailed technical explanation
How to think about this question
The `ROWS` clause defines a physical offset based on row position, which is deterministic and unaffected by gaps or duplicate dates in the data. In contrast, `RANGE` uses logical ordering based on the `ORDER BY` column values, which can lead to variable-sized windows if dates are not unique. For a rolling 30-day average on daily data, `ROWS BETWEEN 29 PRECEDING AND CURRENT ROW` is the safest choice because it guarantees exactly 30 rows per window, assuming one row per day. A real-world scenario where this matters is when a company has missing days (e.g., weekends or holidays) — `RANGE` would include more than 30 rows to cover 30 calendar days, while `ROWS` stays fixed at 30 rows, which may not align with the intended 30-day period.
KKey Concepts to Remember
- Window Frame Clauses
- RANGE BETWEEN
- ROWS BETWEEN
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
Window Frame Clauses
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. Window Frame Clauses 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 — Window Frame Clauses.
What is the correct answer to this question?
The correct answer is: RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW — Option B is correct because `RANGE BETWEEN INTERVAL 30 DAY PRECEDING AND CURRENT ROW` ensures that the window frame includes all rows within the past 30 days, regardless of whether there is exactly one row per day. This is the proper approach for a rolling 30-day average when data may have gaps. Option D (`ROWS BETWEEN 29 PRECEDING AND CURRENT ROW`) assumes a fixed number of rows (30 rows), which only works if each day has exactly one row; if days are missing, the time window will be incorrect.
What should I do if I get this PCDE question wrong?
Review window Frame Clauses, then practise related PCDE questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Window Frame Clauses
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Last reviewed: Jun 30, 2026
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