# For each session, show the previous session's page count using LAG

Canonical URL: <https://datadriven.io/problems/for-each-session-show-the-previous-sessions-page-count-usi-c7dd0285>

Domain: SQL · Difficulty: medium

## Problem

For each session, show the previous session's page count using LAG. If no previous session exists, show 0.

## Related

- [All practice problems](https://datadriven.io/problems)
- [Mock interview mode](https://datadriven.io/interview/for-each-session-show-the-previous-sessions-page-count-usi-c7dd0285)
- [SQL Interview Questions](https://datadriven.io/sql-interview-questions)
- [Data Engineering Interview Prep Guide](https://datadriven.io/data-engineer-interview-prep)
- [Daily Challenge](https://datadriven.io/daily)

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