Write a query to find DAU/MAU ratio from sessions
Last updated: December 2, 2025
Quick Overview
Write a SQL query to calculate DAU/MAU ratio from the sessions table, considering nulls and duplicates.
Elastic
December 2, 202510
5
895 solved
Write a SQL query to calculate DAU/MAU ratio from the sessions table, considering nulls and duplicates.
This question from Elastic'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
- Use advanced SQL features: window functions, CTEs, subqueries
- Write efficient queries that avoid common performance pitfalls
- Handle complex data transformations with multiple joins and aggregations
- Discuss indexing strategy and query optimization
- Address data quality issues: duplicates, missing values, outliers
Key Topics to Cover
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
- How would you validate the correctness of your query results?
- How would you handle slowly changing dimensions in this scenario?
- How would you handle this if the data was spread across multiple databases?
Sharpen Your Skills on Codemia
Practice similar problems with our interactive workspace, get AI feedback, and track your progress.
Practice SQL ProblemsSample Answer
Problem Understanding
The goal is to calculate the Daily Active Users (DAU) and Monthly Active Users (MAU) from the sessions table. DAU is defined as the number of unique users who have sessions on a given day, while MAU...
Approach
- Identify Unique Users: First, we need to extract unique user IDs per day and per month from the
sessionstable. - Calculate DAU: Use a
GROUP BYclause on the date to get the number of ...
Submit Your Answer
