> For the complete documentation index, see [llms.txt](https://docs.whalesync.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.whalesync.com/connectors/google-sheets/foreign-keys.md).

# Foreign keys

Foreign keys allow you to create relationships between tables in your synced Google Sheets.

<figure><img src="/files/Yd6Cn3SwButID1XTeZHB" alt=""><figcaption><p>An example of a foreign key field relating People to Tasks</p></figcaption></figure>

### How to set up foreign keys

#### 1. Define a foreign key column

Create a column in the following format: `Related_[Table Name]`

<figure><img src="/files/fbwhjHCaQdnSescvFVSc" alt=""><figcaption><p>Here our column name is "Related_People" because we're relating Tasks to the People table</p></figcaption></figure>

{% hint style="info" %}
Capitalization matters, so make sure the table name matches exactly.
{% endhint %}

#### 2. Map the Foreign Key field in Whalesync

<figure><img src="/files/ekApGVxMMhZIRwyBavjY" alt=""><figcaption></figcaption></figure>

Google Sheets foreign key fields map with [reference fields](/features/additional-features/reference-fields.md) in other apps.

{% hint style="info" %}
You will likely need to click "Referesh" to ensure Whalesync sees your newest fields
{% endhint %}

#### 3. Insert Foreign Key values

To link a row from another table to your Foreign Key column:

1. Copy the Whalesync ID of the row you want to reference.
2. Paste the Whalesync ID into the foreign key column.

<figure><img src="/files/qqle3QSvKCZ2gaYoBOQ4" alt=""><figcaption><p>Copying the Whalesync ID from a person in the People's table into the "Related_People" column in Tasks</p></figcaption></figure>

* The Whalesync ID is a unique identifier for each row.
* It is Column A in each mapped table in Google Sheets, and it is hidden.
* Click on the arrow to unhide the Whalesync ID column.

{% hint style="warning" %}
**Avoid making any changes to the Whalesync ID column to avoid sync issues.**
{% endhint %}