Compare CSV files by keys and values

First agree on the delimiter, encoding, headers, and which column identifies a row. If row order does not matter, match rows by that stable key before comparing values. If order matters, preserve it in the comparison.

Use CSV diff for structured changes, then inspect added, removed, and changed rows. Watch for duplicate keys, leading zeros, quoted delimiters, and dates that were reformatted. A plain text diff can be useful for exact bytes but may overstate harmless reordering.

Define whether 00123 and 123 are distinct before declaring two files equivalent.