Join orders and transactions to find churn rate

Last updated: April 4, 2026

Quick Overview

Write a query joining orders and rides to produce the combined churn rate.

Coinbase

Data Manipulation (SQL/Python)

Data Scientist

Coinbase

April 4, 2026

Data Scientist

Technical Screen

Data Manipulation (SQL/Python)

Easy

152

590 solved

Write a query joining orders and rides to produce the combined churn rate.

Data manipulation questions at Coinbase test your ability to work with real-world datasets. This Technical 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

Common Table Expressions (CTEs)

Pandas vectorized operations and groupby

Index optimization and query performance

JOIN types and when to use each

Data cleaning and transformation

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 handle slowly changing dimensions in this scenario?
How would you validate the correctness of your query results?
What would you do if this query needs to run every 5 minutes?
How would you handle this if the data was spread across multiple databases?

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Practice SQL Problems

Sample Answer

Problem Understanding

In this scenario, we need to analyze the churn rate by joining the orders and transactions tables. The orders table likely contains information about customer orders, including order IDs and cus...

Approach

Identify Key Columns: Determine the relevant columns in both tables, such as customer_id from both orders and transactions, and possibly order_id and transaction_id for additional con...

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