Docs: recipe for updating a CSV database file from a partial download (#826) - #2153
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…#826) Adds a section to the questions-about-joins page showing how to update matching records of a durable CSV file from a download containing a subset of records and a subset of columns, using join --ul with the database as the left file (right-file values win on collision), plus variants for restoring row order and for keeping database values when the download has empty cells. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
johnkerl
marked this pull request as ready for review
July 9, 2026 19:18
…recipe # Conflicts: # docs/src/questions-about-joins.md # docs/src/questions-about-joins.md.in
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#826
Adds a new section to the questions-about-joins page: updating a durable "database" CSV file from a periodic download that contains a subset of its records and a subset of its columns, with no new records or columns introduced.
The recipe hinges on
join's collision rule -- on paired records, non-join field values from the right file overwrite those from the left file -- so the database goes on the left (-f) and the download on the right, with--ulpassing through database records that received no update. The output schema then automatically matches the database file's columns and column order. Two variants are included:then sort -t idto restore the original row ordering (paired records stream out in download order, unpaired ones after);--rp+putvariant so that empty cells in the download leave the database values alone rather than blanking them out (a pitfall the issue reporter hit directly).All examples are live GENMD samples verified against a fresh build, with two small new sample files
docs/src/data/update-db.csvanddocs/src/data/update-download.csv.🤖 Generated with Claude Code