I imported and prepared the data as described on the Wifi Scanner page.

The main date range is 1st Nov 2019 to Dec 31st 2019 (but also includes up to Jan 5th 2020).

Extracting a basic count of all activity:

SELECT COUNT(mac), DATE(seen_time) FROM wifi_data WHERE DATE(seen_time) BETWEEN '2019-11-01' AND '2020-01-06' GROUP BY DATE(seen_time);

Extracting a basic count of all unique devices:

SELECT COUNT(DISTINCT mac), DATE(seen_time) FROM wifi_data WHERE DATE(seen_time) BETWEEN '2019-11-01' AND '2020-01-06' GROUP BY DATE(seen_time);