Window function: rank over date
Last updated: March 14, 2026
Quick Overview
Use window functions to compute running total partitioned by date.
Airbnb
Data Manipulation (SQL/Python)
Data Scientist
Airbnb
March 14, 2026Data Scientist
Technical Screen
Data Manipulation (SQL/Python)
Easy
72
5
2,169 solved
Use window functions to compute running total partitioned by date.
This question from Airbnb's Technical Screen tests practical data skills. The interviewer wants to see clean, efficient queries that handle edge cases like NULLs, duplicates, and large datasets.
What the Interviewer Expects
- Write syntactically correct SQL with proper JOIN and WHERE clauses
- Use GROUP BY and aggregate functions appropriately
- Handle NULL values correctly in your queries
- Explain the query execution plan at a high level
Key Topics to Cover
Date/time manipulation
Index optimization and query performance
JOIN types and when to use each
Pandas vectorized operations and groupby
Common Table Expressions (CTEs)
Window functions (ROW_NUMBER, RANK, LAG, LEAD)
How to Approach This
- Clarify the schema and expected output format before writing queries.
- Use CTEs (WITH clauses) to break complex queries into readable steps.
- Consider window functions (ROW_NUMBER, RANK, LAG, LEAD) for ranking and sequential analysis.
- Watch for NULLs, duplicates, and edge cases in JOINs and GROUP BY.
- For pandas, prefer vectorized operations over row-by-row iteration.
Possible Follow-up Questions
- What would you do if this query needs to run every 5 minutes?
- How would you optimize this query for a table with 100 million rows?
- Can you rewrite this without using subqueries?
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Practice SQL ProblemsSample Answer
Problem Understanding
In this problem, we are tasked with computing a running total of a specific metric (let's assume it's 'bookings') partitioned by date. The dataset likely includes columns such as 'date' and 'bookings'...
Approach
- Identify the Dataset: Assume we have a table named
bookingswith at least two columns:dateandbookings. - Choose the Window Function: We will use the
SUM()function as a window...
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