Most machine learning engineers are going to have to be conversant with a lot of different data formats. SQL is still one of the key ones used. Your ability to understand how to manipulate SQL databases will be something you’ll most likely need to demonstrate. In this example, you can talk about how foreign keys allow you to match up and join tables together on the primary key of the corresponding table—but just as useful is to talk through how you would think about setting up SQL tables and querying them.