All structured data can be represented as key-value, that includes SQL. They just differ in what constraints are used for the keys and values.

As for your question, NoSQL datastores can be grouped into multiple categories:

- column stores (like hadoop, cassandra, informix), which optimize for sharded and distributed storage of related data elements

- document stores (like elasticsearch), which focus on metadata organization for large opaque (binary) objects

- key-value stores (like redis, openldap), which are basically unstructured, associative arrays (hash maps). They allow the most storage freedom, and are hardest to optimize.

- graph databases (like neo4j, trinity), where more information is carried in annotated inter-object links than in the objects themselves.

Are graph databases key/value? Are document databases key/value?

Try this:

https://en.wikipedia.org/wiki/NoSQL#Types_and_examples_of_No...

https://www.youtube.com/watch?v=qI_g07C_Q5I

No. Triplestores and Graph databases aren't key-value stores. There's more to NOSQL than key value stores although most examples seem to be.