Is it possible to create a chart with data from 2 different tables?
Yes, you have two options you can go custom SQL or Use the Data Hub.
You must be using a data source that allows custom SQL, and enable "Allow Custom SQL" in the data source settings. When designing your chart, use "Custom SQL" when selecting your data source and create a SQL statement to pull columns from your desired tables.
The process to link the table is a join
Example of a inner join: select * from table1 A inner join table2 b on a.id = b.id
From the Data Hub Create Data Sets out of your Data Sources. Once you have the Data Sets created you can go to the ETL tab and select New ETL Job this will take you to the ETL stage. Pull your "E" down to set your extract. Once you have you two extracted data sets on the stage. Pull down the "T" transform. Once on the stage attach the arrows from the extracts. Click on the gear.
Now that your in the join setup you should have some time of ID to join the tables. Just match the two ID columns and save.
Now pull the "L" load to the stage and attach the transformation. Click the gear and walk though the process.
Note: If you want to join more the two tables. Just add your data set and a new join transfromation.
Should look something like this.