I have worked in massive DBs (tables with billions of rows) in both Postgres and MySQL. I occasionally have to look at docs to figure out if what I want to do is supported by the particular version, but that’s about it.
There is a standard SQL, and vendors are free to add to it. Generally speaking, though, you can get quite far with the standard.
> there is no serious application development without having to delve into the sanctum sanctorum of your database vendor.
OK? I could say the same thing about needing to intimately know the differences in C++ versions. Yes, you should know your tools well.
One huge problem is that learning SQL will take you nowhere, unless your schema consists of a few tables with a handful of rows at most.
There is no standard SQL, and there is no serious application development without having to delve into the sanctum sanctorum of your database vendor.