# Why do I need an ID column?

To enable two-way sync between Supabase and your other apps, Whalesync needs a way to uniquely identify each record in your Supabase database.

If your table already has a unique primary key, Whalesync will use it.

If not, Whalesync will automatically add a whalesync\_postgres\_id column to ensure each record can be tracked reliably.

<figure><img src="/files/3IowpEKyLZg8zTpxieXl" alt=""><figcaption><p>What the automatically added "whalesync_postgres_id" column looks like in Supabase</p></figcaption></figure>

Alternatively, if you'd prefer to add your unique ID field manually, you can follow these steps:

{% content-ref url="/pages/kmoit3oru7EZjPKo3YS3" %}
[Adding default values to primary keys](/connectors/supabase/adding-default-values-to-primary-keys.md)
{% endcontent-ref %}


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