Why Google's BigTable referred as a NoSQL database?

Question

From Wikipedia:

Notable production implementations [of NoSQL databases] include Google\'s BigTable, Amazon\'s Dynamo and Cassandra.

Answer 1

When people say "NoSQL" what they generally mean is "non-relational". To the best of my knowledge BigTable does not feature primary / foreign keys, JOINs, or relational calculus of any type.

The fact that BigTable features a query syntax that includes the words "SELECT" and "WHERE" does not mean it adheres to the principles of relational databases. It's more of a convenience, or a "hook", to make single-entity-type matches more familiar to programmers coming from relational databases.