Tools for Daily

Home / Excel & CSV / CSV Left Join by Identifier

Working browser tool

CSV Left Join by Identifier

Perform a bounded left join by first-column key; report unmatched IDs; reject duplicate lookup keys.

Enter your values

Your inputs are processed locally. Review the method and limitations before relying on the estimate.

First row must contain these exact column names: id, name. Your text stays in this browser. Export JSON/CSV for your own backup; no automatic cloud saving.

For the second input table, type exactly ---SECOND--- on its own line after your first CSV table, then add the second CSV table including its header row (as shown in the example).

Local save is optional and stays on this device; do not save sensitive information on shared devices.

How does CSV Left Join by Identifier work?

Perform a bounded left join by first-column key; report unmatched IDs; reject duplicate lookup keys.

Worked example

Edit the sample rows, process them locally, inspect validation results and download the output.

Frequently asked questions

Is my data transmitted to Tools for Daily?

No. The tool is browser-local; there is no application upload request.

Are the results permanently stored?

No. Export a copy. Any optional browser-only save remains on this device and can be cleared.