---
title: Find the same company in two lists
description: Ask whether two entries name the same company, for each pair from two lists, and split the pairs into matches, non-matches and pairs for a person.
goal: A developer joining two lists of companies leaves with the pairs that match, the pairs that don't, and the unclear pairs in a file for a person.
reader: A developer cleaning or joining two lists of companies whose names and addresses are spelled differently
kind: how-to
verified: 2026-11-03
---

# Find the same company in two lists

At the end, you have the pairs that name the same company in one file, and the pairs ThinkThen is not sure about in another for a person.

## 1. Put the candidate pairs in a file

Build the pairs with ordinary code first, such as entries that share a city or a postcode. Each pair is one question, so asking about every possible pair costs far more.

Write one pair per line, with both sides under one field, `pair`, so the model reads them together:

```json title="pairs.jsonl"
{"id":"p1","pair":{"left":"Example Group Ltd, 12 High St, Leeds","right":"Example Grp, 12 High Street, Leeds"}}
{"id":"p2","pair":{"left":"Example Group Ltd, 12 High St, Leeds","right":"Sample Holdings, 4 Mill Lane, York"}}
{"id":"p3","pair":{"left":"Northwind Traders, Seattle","right":"Northwind, Seattle WA"}}
{"id":"p4","pair":{"left":"Contoso Ltd, Paris","right":"Contoso Group, Lyon"}}
```

## 2. Ask whether each pair names the same company

`--field /pair` sends both sides as one text. The low and high bars send an unclear pair to not sure, and `--into same` adds the answer to each line:

```sh
thinkthen decide --field /pair --low 0.2 --high 0.8 \
  --into same 'Do left and right name the same company?' \
  pairs.jsonl > matched.jsonl
jq -c '{id, same}' matched.jsonl
```

Output

```text
{"id":"p1","same":true}
{"id":"p2","same":false}
{"id":"p3","same":true}
{"id":"p4","same":"unsure"}
```


The first and third pairs spell one company two ways. The second names two companies. The fourth shares a name but not a city, so the model is not sure.

## 3. Keep the matches and set aside the unclear pairs

`same.jsonl` gets the matches, ready to join. `person.jsonl` gets the not-sure and failed pairs:

```sh
jq -c 'select(.same == true) | .pair' matched.jsonl \
  > same.jsonl
jq -c 'select(.same == null or .same == "unsure") | .pair' \
  matched.jsonl > person.jsonl
cat person.jsonl
```

Output

```text
{"left":"Contoso Ltd, Paris","right":"Contoso Group, Lyon"}
```


The Contoso pair is the one a person decides. Never count a not-sure or failed pair as a match or a non-match by default.

## Check the result

- Label a sample of pairs yourself and compare, as [Measure answers against your own labels](/how-tos/measure-answers-against-your-own-labels/) shows.
- A wrong yes merges two different companies. If you find one, widen the gap between the bars, so more pairs go to a person.

## Next

[Break a problem into decisions](/how-tos/break-a-problem-into-decisions/) shows how to split a larger job into questions like this one.