Write a query to find DAU/MAU ratio from products
Last updated: January 10, 2026
Quick Overview
Write a SQL query to calculate DAU/MAU ratio from the products table, considering nulls and duplicates.
Neon
January 10, 2026119
4
1,820 solved
Write a SQL query to calculate DAU/MAU ratio from the products table, considering nulls and duplicates.
Data manipulation questions at Neon test your ability to work with real-world datasets. This Phone Screen question evaluates your SQL proficiency, understanding of data modeling, and ability to derive insights from raw data.
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
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 optimize this query for a table with 100 million rows?
- How would you validate the correctness of your query results?
- What indexes would you create to support this query?
- How would you handle slowly changing dimensions in this scenario?
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Practice SQL ProblemsSample Answer
Problem Understanding
To calculate the Daily Active Users (DAU) and Monthly Active Users (MAU) ratio from the 'products' table, we need to understand the structure of the data involved. The 'products' table likely contains...
Approach
- Identify Unique Users: First, we need to calculate DAU by grouping the data by
activity_dateand counting distinctuser_ids. - Calculate MAU: Next, we calculate MAU by grouping the d...
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