# Set up uniqueness in Resource

Suppose we want to store the Patient resource only if a patient with such an email does not already exist in the database. Hence, we need to make `Patient.telecom.value` unique where `Patient.telecom.system = 'email'`.

## Create Unique Index

To solve the problem, we can use PostgreSQL [unique indexes](https://www.postgresql.org/docs/current/indexes-unique.html).

```sql
CREATE UNIQUE INDEX patient_email_unique_idx1
ON patient ((jsonb_path_query_first(resource, '$.telecom[*] ? (@.system == "email").value') #>> '{}'));
```

In this example [jsonb\_path\_query\_first](https://www.postgresql.org/docs/15/functions-json.html) PostgreSQL function will check the first email in Patient.telecom array. This works if the Patient resource can have only one email.

If it can have two or more emails, the only solution we see is to create a new `patient_email` table, store emails into it via [PostgreSQL triggers ](https://www.postgresql.org/docs/current/sql-createtrigger.html)when inserting/updating in `patient` table and make Unique index for `patient_email` as in the example above.