# Combine user_ids from transactions and user_sessions using UNION ALL in a CTE

Canonical URL: <https://datadriven.io/problems/combine-userids-from-transactions-and-usersessions-using-u-dc72c2cd>

Domain: SQL · Difficulty: medium

## Problem

Combine user_ids from transactions and user_sessions using UNION ALL in a CTE. Then count total rows and non-NULL user_ids.

## Related

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