Atomicity Consistency Isolation Durability (ACID)

At a high level, SQL and NoSQL comply with separate rules for resolving transactions. RDBMSs must exhibit four “ACID” properties:

• Atomicity means all transactions must succeed or fail completely. They cannot be partially-complete, even in the case of system failure.
• Consistency means that at each step the database follows invariants: rules which validate and prevent corruption.
• Isolation prevents concurrent transactions from affecting each other. Transactions must result in the same final state as if they were run sequentially, even if they were run in parallel.
• Durability makes transactions final. Even system failure cannot roll-back the effects of a successful transaction.