Simply put:
What is a relational database?
Based on the relational model to build, there are the associations between different table or library
What is non-relational database?
No associated between different table or library, to establish the basis of non-relationship model
Relational databases and non-relational databases their own characteristics:
the RDBMS:
two-dimensional table
data access through SQL
strong data security aspects
NoSQL:
focus on high-performance, high concurrency, flexibility, etc.
Let me talk about advantages and disadvantages:
powerful query features - strong consistency - two indexes: the advantages of relational, non-relational shortcomings of
flexible models - Scalability - Performance: non-relational form of advantage, relationship type of disadvantages
NoSQL classification and typical products:
key (KV) store: Memcached, Redis
column stores (column-oriented): HBASE (Sina, 360), Cassandra (200 server cluster)
document database (document-oriented): MongoDB ( NoSQL) closest to the relational database of
graphics memory (Graph): Neo4j