How to write queries

Valid queries MUST expose an `external_id` column or an `email` column. Lines with no `external_id` or `email` will be ignored.
All other fields will be imported as traits on the matching users.
For example, the following query will map the column `users.id` to your Hull users' `external_id`.

                    SELECT user_id as external_id, plan_name, monthly_amount FROM users_subscriptions
                  

Using incremental queries

You can run incremental queries based on the date of the last sync.
The query will be rewritten to replace :last_updated_at with the date of the last successful sync operation.

For example to import entries from a users table with a date column named updated_at, you can write :

                    SELECT id as external_id, email as email, firstname as first_name
                    FROM users
                    WHERE updated_at >= :last_updated_at