按日期间隔按序列号分组的平均温度

So, I'm a bit stuck trying to calculate averages in a MySQL query. What I'm trying to do is read the data from two tables, one of which is small and has entries describing the room, serial number, elevation, and other data about a sensor. The other table contains the recordings of the temperature output for each serial number. Here's some sample data for each table.So, I'm a bit stuck trying to calculate average