SQLite is a popular relational database management system that supports the ACID properties. ACID is an acronym for Atomicity, Consistency, Isolation, and Durability, which are the fundamental principles for ensuring the reliability and consistency of database transactions.
Atomicity
Atomicity refers to the principle that a transaction must be treated as a single, indivisible unit of work. If any part of the transaction fails, the entire transaction should be rolled back, so that the database is left in the same state as it was before the transaction began. SQLite ensures atomicity by using a journaling system that records all changes to the database before they are made, and then applying those changes in a single operation when the transaction is committed.
Consistency
Consistency refers to the principle that the database must always be in a valid state, meaning that all constraints and rules defined by the database schema are followed. If a transaction violates any of these rules, the transaction must be rolled back. SQLite enforces consistency by checking for rule violations before committing the transaction and ensuring that all changes made by a transaction are consistent with the database schema.
Isolation
Isolation refers to the principle that concurrent transactions must be isolated from each other, so that each transaction appears to execute in isolation, even if there are other concurrent transactions occurring at the same time. SQLite provides isolation by using locks to prevent concurrent transactions from modifying the same data simultaneously. This ensures that each transaction is executed in isolation and produces a consistent result.
Durability
Durability refers to the principle that once a transaction is committed, the changes made by that transaction must be permanent and survive system failures, power outages, or other events that might cause the system to crash. SQLite ensures durability by using a write-ahead logging mechanism, which records all changes made to the database in a separate file. This log can be used to recover the database in the event of a failure, so that the database can be restored to its last consistent state.
In summary, SQLite is a reliable and consistent database management system that supports the ACID properties. It provides atomicity, consistency, isolation, and durability to ensure that transactions are executed correctly and that the database remains in a valid and consistent state at all times.