Not required, but knowing a little relational algebra helps queries make a lot more sense. A lot of the features like constraints and indices are very thin vene

Not required, but knowing a little relational algebra helps queries make a lot more sense. A lot of the features like constraints and indices are very thin veneer over the underlying concepts. At the other end of the spectrum, once you can write a few basic queries check out something like SQL Murder Mystery https://mystery.knightlab.com/ https://mystery.knightlab.com/ This one is super-fun and lets you practice some basic to low-intermediate skills.