HI, I want to learn different database like MySQL, PostgreSQL, MongoDB etc, are there any website of your knowledge where I can learn concept and do exercises like Exercism?
PostgreSQL exercises has a good amount of exercises with tests, but it is geared mostly toward teaching SQL, as opposed to PostgreSQL flavor vs other SQL flavors.
HackrRank has a decent SQL Track that supports several flavors - Oracle, DB2, MySQL, and SQLServer. But again, its mostly to teach SQL, as opposed to the differences.