NoSQL is short for not only SQL (does not mean there is no SQL).

Common features of NoSQL include:

• Horizontal scaling (adding more computers)
• Replicated and distributed data
• Weaker concurrency (generally not ACID)

Comparing SQL and NoSQL:

SQL conforms to ACID, as it is the “gold standard” for RBDMS:

• Atomicity
• Consistency
• Isolation
• Durability

NoSQL generally conforms to BASE - “good enough” for NoSQL:

• Basically
• Available
• Soft State
  • State may change even without “triggering” input
• Eventually Consistent
  • Update may result in inconsistent state, but will eventually become consistent

There are also different types of databases which are typically used with SQL and NoSQL:

• SQL
  • Relational (OLTP) database
  • Analytical (OLAP) database
    • Not necessarily relational
    • Star schema - makes hypercube out of relations