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Data Deduplication Fundamentals
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Data Deduplication Fundamentals

MediumSQL · PostgreSQL

Problem

What is data deduplication?

In this task, treat duplicate backup-job records as rows that share the same job_name and repository_name. Write a SQL query to return one canonical row per duplicate set, keeping the most recent record by last_seen_at, and breaking ties by the highest job_id.

Output

  1. One row per duplicate set, with columns job_name, repository_name, job_id, last_seen_at, and status
  2. Include only groups that have more than one row
  3. Keep the most recent row in each group, and if last_seen_at ties, keep the row with the highest job_id
  4. Sort by job_name, then repository_name

Schema

backup_jobs
ColumnTypeDescription
job_idPKINTUnique backup job record identifier
job_nameVARCHAR(100)Backup job name
repository_nameVARCHAR(100)Repository where the job stores backups
last_seen_atTIMESTAMPMost recent time this record was observed
statusVARCHAR(30)Current job status
Tablesbackup_jobs
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