Not every person learns the same way without a doubt. However, unless you can measure (or test) for that, how can we tell what teachers are adding value to or not the the educational experience.

The perception that MySQL is smaller and faster than PostgreSQL is bullshit. PostgreSQL is actually smaller than MySQL even though it has many more features. In my experience Postgres's query planner is light-years ahead of MySQL. The result is that PG is almost always faster than MySQL in the general case. MySQL is also loaded with gotcha's and odd behaviour based on the "back end" or what settings you use.

When were those olden days? I've been using PostgreSQL in production since 2001 because MySQL was (and is) relatively unstable and has an incomplete set of SQL features. Postgres has always been way more stable than MySQL. IMHO, PG is also way more straightforward than MySQL, MS SQL and Oracle. MySQL in particular has loads of hidden tricks and gotcha's. For example, referential integrity.

I've programmed and maintained a number of "Pick" applications as well as applications using SQL databases such as PostgreSQL. I think of Pick as a poor implementation of a poor idea. You can easily get yourself in trouble designing multi-value databases in Pick. You'll always be jumping into procedure land to cull through your data. Even with ideal table design (called files in Pick), try doing a sub select. Or an outer join with a having clause. The only nice think I could say about Pick and it's variants is that with low order data sets, applications and hardware, pick was very efficient.