So confused

I really have no idea that
I am writing Oracle SQL
And it can run!
Then setting up database connection
Scheduling batch job
Tracking size and speed
How come I can do that?
So technical that like I am working on the school project
Which I never touch upon after school…for how many years…

Then I am calculating the price of derivatives
Formulating the rate of inverse floaters
Determining which one has no credit loss
But none of those I can solve
Those that I used to score the full marks
For just, what, less then 4 months before
How come I cannot do that?