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Shopify·Data Analyst·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Jun 2026Remote

Summary

Shopify SQL round, one question, pretty focused on date handling which I didn't think would matter as much as it did.

Questions Asked (1)

Q1

Using only the sessions table, write a SQL query that returns session counts grouped by day, with columns (day, session_count) ordered by day. Handle the timestamp truncation and any timezone concerns appropriately.

Product Analytics & MetricsData Modeling
Author's notes

I jumped straight to DATE_TRUNC and felt pretty good about it, but then they asked how I'd handle timezones and I kind of stumbled.

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AI HintsAI Generated

Suggested Approach

First, clarify the timezone assumption (e.g., UTC or business local time) and the definition of a 'day'. Then, write a query that truncates the session timestamp to the day level, groups by that truncated date, counts sessions, and orders by day. Use appropriate date functions like DATE_TRUNC or CAST to DATE, and consider timezone conversion if needed.

Pro tip: Always state your timezone assumption explicitly and mention that you would confirm it with stakeholders, as this can significantly impact daily metrics. Also, consider using a date spine to include days with zero sessions if the business needs a complete time series.

1. Clarify requirements and assumptions

Ask about the timezone (e.g., UTC, store local time) and whether days with zero sessions should be included. Confirm the granularity (daily) and ordering.

2. Choose the date truncation method

Decide between DATE_TRUNC('day', timestamp) or CAST(timestamp AS DATE) based on the SQL dialect. If timezone conversion is needed, apply AT TIME ZONE before truncation.

3. Write the aggregation query

Select the truncated date as day, count(*) as session_count, group by day, and order by day ascending.

4. Consider edge cases and performance

If zero-session days are required, left join with a date spine. Ensure the query uses indexes efficiently and mention any performance considerations.

Key Points to Mention

  • Timezone handling: convert timestamps to the desired timezone before truncation.
  • Date truncation function: DATE_TRUNC('day', timestamp) or CAST(timestamp AS DATE).
  • Grouping and ordering: GROUP BY day ORDER BY day.
  • Counting sessions: use COUNT(*) or COUNT(session_id) depending on table structure.
  • Zero-session days: optionally use a date spine and LEFT JOIN to include them.
  • Performance: avoid functions on the timestamp column in WHERE clauses if filtering, and consider indexing.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.