That's entirely subjective to the person conducting the interview on what those basics are. I've never interviewed someone who didn't know what a racket is for a tennis player for example unless their resume was entirely fabricated and or they really didn't play tennis as a tennis player.

I know from your past posts it's more along the lines that they did not play tennis as a tennis player in regards to for example, senior DBA's not knowing how to get the system time. But that's your professional opinion on what those basics should entail to be above average for that position. I used to think it was a huge deal. But now, I've come to realize that I personally do not care about memory capacity of mundane syntax that is insanely easy to lookup on your own. I myself could likely fail to know some basics you may find as a need-to-know for those basics as well. It doesn't negate the fact that I am a data architect who has developed complex data platforms from scratch because I have the ability to solve problems on my own.  And therefore, be paid above average.

I'm sure you could tell that I am a type of interviewer who cares less about code tests, coding on whiteboards and all that jive. I'm more interested in what problems you have solved, if you could tackle the problems we need solving, and how you may have solved the problems in the past we are facing as a business. Then the difference between a DBA and a Senior DBA is just how much more exposure to those problems you have had along with your ability to move into a leadership role as your next career steps. I.e.: if the only difference between your seniors and your normal employees is one knows how to get system time and the other does not, then that's not enough to separate between a senior or not.