01
Data Models
- Relational databases organize information into relations and tuples.
- Document stores represent records as structured documents.
- Key-value stores associate keys with values.
- Graph databases represent entities and relationships explicitly.
- Column-oriented systems optimize particular analytical workloads.
02
Relational Systems
SQL provides declarative mechanisms for querying and manipulating relational data. The database engine determines an execution strategy rather than requiring users to specify every low-level operation.
03
Transactions
Transactions group operations into logical units. The classical ACID properties describe atomicity, consistency, isolation, and durability.
- Atomicity: a transaction is treated as an all-or-nothing unit.
- Consistency: transactions preserve defined integrity constraints.
- Isolation: concurrent execution is controlled to satisfy the chosen isolation semantics.
- Durability: committed state survives appropriate failures.