That's an absurd line of thinking. First, Course has no SQL courses [1]. Second, just because "x" sells cheaply somewhere (or is given away) does not automatically make all other content creators fall in line. You obviously are not familiar with Chris Date's work. His book sells for $150 still [2] so I'm actually surprised to see his video courses sell for less than $500. And I know I'm not alone in chuckling at your "the era of Coursera" comment haha. Idealism at its finest!
There is steady downwards pressure on all video based education. Saying SQL is not on Coursera today is like saying, "I can't find the complete works of Hemmingway on Amazon" in 1995. Chuckle if you want, but the trend is your friend.
