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Product guide · 5 min read

Finding duplicates in CSV files without a database

Sort by candidate keys, scan runs, and use filters, lightweight dedup recon before SQL DISTINCT.

Published March 21, 2025 · Table

Without SQL, sort by the natural key (email, order_id, device_id) and look for adjacent identical keys. For composite keys, concatenate in a scratch column or sort by multiple columns.

Limits

  • Case sensitivity can hide dupes, normalize case upstream.
  • Trailing spaces break key equality.

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