Join and Dedup — Solution & ExplanationProblems / Join and Dedup / EditorialApproach

Use a CTE with ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY login_time DESC) to rank each user's logins.

Filter for rn = 1 to get only the latest login per user.

JOIN with users to get the profile details.

Key InsightThis is the dedup-then-join pattern. When a fact table has multiple rows per entity and you only want the latest (or earliest, or max, etc.), first deduplicate using ROW_NUMBER, then join. User 7 (grace) has no logins so doesn't appear.Hints

Use ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY login_time DESC) to rank logins per user.

Filter for rn = 1 to keep only the most recent login per user.

Then JOIN this deduplicated result with the users table.

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