I wasn't great a sports, but one lesson that stuck with me was practice how you plan to play. You only get better if you actively practice writing good code. As far as I know, there is no such thing as a "joint" table. However, join tables are pretty common, and fairly important in database development. Join tables are really useful for constructing relations. Even a company with 3,000 employees needs to be mindful of the efficiency of their code.
Another thing that you mention that is concerning is that you've worked on hundereds of things this year. There's not enough time in the day to work on hundereds of things in a year with any sort of depth beyond copying and pasting from Stack Overflow or blog tutorials.
Employeers are looking for skills demonstrated intentionally, and some specialization in something that they need. You spend more time cleaning up after generalist "rock stars" than someone who has a defined focus.