You can try the one offered by University of San Diego on Coursera if you're a beginner.
For an intermediate level you can try the one offered by Google cloud (on coursera)
Surely go for hadoop, if you have knowledge of Oracle then it would be great !
Checkout Udemy. I did one course from Coursera. Although the Course was really interesting but I didn’t recieved the certificate. I tried to pay the money a lot of times. But the transactions failed. So my experience with Coursera isn’t good.