Exercise

Joining themes to their grandchildren

We can go a step further than looking at themes and their children. Some themes actually have grandchildren: their children's children.

Here, we can inner join themes to a filtered version of itself again to establish a connection between our last join's children and their children.

Instructions

100 XP

Use another inner join to combine themes again with itself.
- Be sure to use the suffixes "_parent" and "_grandchild" so the columns in the resulting table are clear.
- Update the by argument to specify the correct columns to join on. If you're unsure of what columns to join on, it might help to look at the result of the first join to get a feel for it.