> For the complete documentation index, see [llms.txt](https://docs.subsalt.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.subsalt.io/configuration/creating-synthetic-databases/patient-identifiers.md).

# Patient identifiers

To build the database we require that you identify the field that represents a single patient.

This allows our system to count the number of patients in the dataset, which is crucial for accurate privacy evaluations.

### Setting the identifier

As a part of onboarding your database you will be prompted to set a patient identifier right after you have configured your tables.

To set the identifier, select the `Patient Table` and `Patient ID Field` that represent one patient.

Typically this will be a dedicated "patients" table with one row per patient, but if that's not how your database is structured it's also okay for this to be a table like "visits" that still captures the patient IDs.

After you've selected the correct table and field, press `Save` and you're ready to continue with onboarding.

### Updating the identifier

If you need to can change your patient identifier after the fact you can by navigating to the `Settings` tab in your database. Once you change the table and field, press `Save`.


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