I tried to step through this logic in an ETL for you. I think that some of this is more complicated in ETL vs MySQL, but here goes.
There are four main steps.
Step 1: Assign a value for the date you want to compare to. In your case, you mentioned 30 days prior and 1 day prior. In ETL I used the "Date Operations Tile" to create two new fields, Date-30 and Date-1.
Step 2: You need to join these dates to your original data set and then remove the duplicate (Date_1) field.
Step 3: Lookup the number of fans from 30 days ago and join that to your data.
Step 4: Repeat step 3, but for one day ago.
Finish the ETL by attaching an output data set tile and naming your new data set.
This will give you a data set with the following schema:
Good luck to you. Let me know if you have questions.