What does acid in mysql mean?

ACID in MySQL includes atomicity, consistency, isolation and durability. Atomicity ensures that all transactions succeed or fail; consistency ensures that the database state remains consistent before and after the transaction; isolation ensures that concurrent transactions do not affect each other; and durability ensures that submitted modifications are permanently saved.

ACID in MySQL

What is ACID

ACID They are the four major characteristics of database transactions, namely atomicity, consistency, isolation, and durability.

Atomicity

Atomicity means that a transaction is an indivisible unit, either all executions succeed or all fail. During transaction execution, even if an error occurs, the database will not be in an intermediate state.

Consistency

Consistency means that the database state remains consistent before and after the transaction is executed. When a transaction starts, the database is in a consistent state, and when the transaction ends, the database is still in a consistent state.

Isolation

Isolation means that concurrent transactions do not affect each other. Each transaction considers itself to be executed independently and not affected by other transactions.

Persistence

Persistence means that once a transaction is committed, its modifications to the database will be permanently saved, even if the system crashes or fails.

ACID in MySQL

MySQL supports transactions and follows ACID properties.

• Atomicity: MySQL uses redo logs and undo logs to ensure atomicity. The redo log records changes in transaction execution, and the undo log records the state before transaction execution. When a transaction commits, the redo log applies the changes to the database, ensuring that the transaction is indivisible.
• Consistency: MySQL uses constraints (such as foreign key constraints) and triggers to maintain consistency. Constraints ensure that data conforms to predefined rules, and triggers perform automatic actions when specific events occur to maintain the integrity of the database.
• Isolation: MySQL uses a locking mechanism to achieve isolation. When a transaction accesses data, the data is locked to prevent other transactions from concurrently modifying the same data.
• Persistence: MySQL writes transaction-committed modifications to the redo log and data files. Even if the system crashes, committed changes can be restored from the log after a reboot.

The above is the detailed content of What does acid in mysql mean?. For more information, please follow other related articles on the PHP Chinese website!