Using LEFT JOIN of users to transactions, return user_id and COALESCE(COUNT(t.transaction_id), 0) AS

A medium SQL mock interview question on DataDriven. Practice with AI-powered feedback, real code execution, and a hire/no-hire decision.

Domain

SQL

Difficulty

medium

Interview Prompt

Using LEFT JOIN of users to transactions, return user_id and COALESCE(COUNT(t.transaction_id), 0) AS tx_count (users with no transactions get 0). Group by user_id. Order by tx_count ASC, user_id.

How This Interview Works

1. Read the vague prompt (just like a real interview)
2. Ask clarifying questions to the AI interviewer
3. Write your sql solution with real code execution
4. Get instant feedback and a hire/no-hire decision