Welcome to your interview for the Customer Insights Analyst role at Google.
The question is on your right: Prevent Metric Inflation in Joins. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen. You have three graded attempts to score 7/10 or better.
In analytics work at Google, many datasets are not at the same grain. For example, a Google Ads campaign can map to multiple labels, and a conversion can be associated with multiple touchpoints. If you join these tables directly, your counts and sums can inflate.
Explain how you would handle a many-to-many join in SQL without inflating metrics. Your answer should cover:
The interviewer is not looking for obscure syntax. They want a clear explanation of table grain, deduplication strategy, and when to pre-aggregate or use an intermediate mapping table before joining. Use simple PostgreSQL examples where helpful, and frame your answer around common analytics reporting problems.