ByteDance
Medium
Data ScientistSelect max-discount product per category
Data Manipulation (SQL/Python)
0
0
October 13, 2025
SQL Window Function Interview Questions
Window function questions test how you compute row-level metrics while keeping the original rows.
Expect ROW_NUMBER, RANK, LAG, LEAD, and running totals with PARTITION BY and ORDER BY.
Interviewers want clear reasoning about partitions, ordering, and edge cases.
53Questions
21Companies
Common SQL window function interview patterns
- Top N per group using ROW_NUMBER
- Running totals and cumulative sums
- LAG/LEAD for previous and next values
- Ranking ties with RANK vs DENSE_RANK
- Window + aggregation combinations
- Moving averages over time windows
SQL window function interview questions
Filter and sort
DoorDash
Medium
Data ScientistCompute rolling cold-delivery rates with windows
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Amazon
Medium
Data ScientistFind top-spend categories per customer with ranking
Data Manipulation (SQL/Python)
0
0
October 13, 2025
DoorDash
Medium
Data ScientistWrite SQL for percent and window changes
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Google
Medium
Data ScientistCompute monthly CRR with merges and gaps
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Capital One
Medium
Data ScientistWrite SQL to find top net-revenue products
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Chime
Medium
Data ScientistWrite rolling-window SQL over weekly cohorts
Data Manipulation (SQL/Python)
0
0
October 13, 2025
DoorDash
Medium
Data ScientistWrite SQL for cold-complaint diagnostics with LAG/QUALIFY
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Snowflake
Medium
Data ScientistDesign an analytic warehouse for event data
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Snowflake
Medium
Data ScientistBuild a cohort dashboard with Streamlit and SQL
Data Manipulation (SQL/Python)
0
0
October 13, 2025
TikTok
Medium
Data ScientistCompute last-to-previous ad impression gaps
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Snowflake
Medium
Data ScientistQuery seven-day conversion with windows and dedupe
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Robinhood
Medium
Data ScientistWrite SQL and Python for transaction analytics
Data Manipulation (SQL/Python)
0
0
October 13, 2025
TikTok
Medium
Data ScientistCompare SQL counts, windows, and NULL semantics
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Meta
Medium
Data ScientistDefine and analyze new-vs-existing activity
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Pinterest
Medium
Data ScientistWrite windowed retention and ARPU SQL
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Amazon
Medium
Data ScientistDesign SQL/Pandas aggregations on retail schema
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Thumbtack
Medium
Data ScientistWrite complex joins and window functions
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Atlassian
Medium
Data ScientistRank each team’s top 3 scores in 2024
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Flatiron Health
Medium
Data ScientistCompute churn metrics and rank top students
Data Manipulation (SQL/Python)
0
0
October 13, 2025
Common mistakes with SQL window functions
- Missing PARTITION BY or ORDER BY
- Using RANK when ROW_NUMBER is required
- Incorrect window frames for running metrics
- Combining aggregates and windows incorrectly
- Ignoring NULL ordering behavior
How window function questions are evaluated in interviews
Interviewers prioritize correctness and the right partitioning logic.
Explain why you chose a window function instead of a GROUP BY.
Be clear about ordering and how ties are handled.