Welcome @gianlucaf81
This type of graph question has come up a few times, and the best solution that I found was to use Flux (not InfluxQL, as you are using). Here is what I did to create a month-over-month view. You would do the same using yesterday-vs-today.
While not as ideal as having both data sets in one graph, you could stay with InfluxQL and just create two panels (arranged top over bottom) with one set to always display the time from 24 hours earlier than the other.