# 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`. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.subsalt.io/configuration/creating-synthetic-databases/patient-identifiers.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.