SQL vs NoSQL

DBMS (Database Management System)

software layer, or service
provides read/write access to databases
- client/server model
centralized database administration (DBA)
- reliability, availability

Relational (SQL) vs Non-Relational (NoSQL)

SQL: structured data, tables, rows, columns
- MySQL, PostgreSQL, SQLite
NoSQL: unstructured data, key-value pairs, documents, graphs
- MongoDB, CouchDB, Cassandra

Consistency

Can delayed transactions leave the DB in an inconsistent state?
ACID (relational)
- atomic: all commits succeed/ fail as one
- consistent: when transaction completes
- isolated: transactions run one at a time
- durable: transaction results are permanent
BASE (NoSQL)
- basically available: appears to function properly
- soft state: state can change, without input
- eventually consistent at read time

DB Schema

Design of your data
how your data is organized
types of entities
- attributes
- relations
derived from Data Model
SQL vs NoSQL differences
- SQL: schema on write
- NoSQL: schema on read