CSV Join and Merge Planner

Plan and preview a join between two CSV files.

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CSV Join and Merge Planner

How to use this tool

  1. Paste both CSV files, each with a header row, and name the column they share.
  2. Choose left or inner join, then press Plan join to see row counts and a preview.
  3. Use Load sample: left rows Ana (id 1) and Bo (id 2), right row Oslo (id 1) only.

Worked example

Left-joining the sample on id gives 2 rows: Ana with Oslo, and Bo with an empty city, because id 2 has no right-side match. An inner join on the same data gives 1 row, Ana with Oslo, because Bo's row is dropped. The planner reports both counts before you copy anything.

What this tool does not do / Limits

The planner joins on exact text matches in one shared column and previews the first 50 joined rows. It does not fuzzy-match names, does not handle many-to-many explosions beyond listing each combination, and is a planning preview, not a database — check the counts against your real data before importing anywhere.

Frequently asked questions

What is the difference between left and inner?

Left keeps every left row and leaves blanks where there is no match. Inner keeps only rows that match on both sides.

What if the key column is missing?

The tool reports the missing column by name instead of guessing a different column.

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