Theory

https://en.wikipedia.org/wiki/CAP_theorem

https://en.wikipedia.org/wiki/Shard_%28database_architecture%29: split rows across servers

SQL vs NoSQL

http://stackoverflow.com/questions/2559411/sql-mysql-vs-nosql-couchdb

http://stackoverflow.com/questions/4048151/what-are-the-options-for-storing-hierarchical-data-in-a-relational-database

https://en.wikipedia.org/wiki/Hierarchical_and_recursive_queries_in_SQL

http://www.nosql-vs-sql.com/

Vertical vs horizontal scaling

• http://stackoverflow.com/questions/5401992/what-does-scale-horizontally-and-scale-vertically-mean
• http://stackoverflow.com/questions/11707879/difference-between-scaling-horizontally-and-vertically-for-databases
• https://en.wikipedia.org/wiki/Scalability#Horizontal_and_vertical_scaling:

Summary:

• horizontal: add more servers

  NoSQL does it better than relational. TODO why?

• vertical: make one server more powerful.

  Relational databases do it better than NoSQL. TODO why?

DDL

DML

http://stackoverflow.com/questions/2578194/what-is-ddl-and-dml