First there is so much value in this post for new users:
@amaster507 also came from a sql background too.
Beyond that, it is difficult to forget what you know concerning rows/tables. Here is a learning course made just for you:
https://dgraph.io/learn/courses/datamodel/sql-to-dgraph/overview/introduction/
And also check out
https://dgraph.io/learn/courses/datamodel/evolution/overview/introduction/
these courses focus on the GraphQL but as DQL is the core under the GraphQL API endpoint it very much applies to DQL in general as well.
@chewxy wrote a blog that gets down to some of the lower level concepts of Dgraph too: