This article focuses on interviews. In interviews, you only need to answer the key points. You do not need to have a very in-depth answer to the framework. If you want to cope with the interview, it is enough. Grasp the key points.
Interviewer: What is the principle of MySQL transactions?
The principle of MySQL transactions is based on ACID (atomicity, consistency, isolation, durability) characteristics. The specific principles are as follows:
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Atomicity: The smallest execution unit of a transaction is an atomic operation, either all executions succeed, or all rollbacks fail. Before a transaction begins, MySQL assigns a unique identifier to the transaction and records the transaction's start status in the undo log. All operations in the transaction will be recorded in the redo log and undo log for use in rollback or recovery operations.
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Consistency: The state of the database must remain consistent before and after transaction execution. MySQL achieves consistency by dividing all modification operations into multiple stages. Before performing modification operations, the relevant data will be locked to ensure that other transactions cannot modify the same data at the same time, thereby avoiding data inconsistency problems.
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Isolation: MySQL supports multiple isolation levels (read uncommitted, read committed, repeatable read and serialization), and controls the visibility and concurrency behavior between transactions through isolation levels. MySQL uses concurrency control mechanisms such as locks and MVCC to achieve isolation. The lock mechanism can prevent multiple transactions from modifying the same data at the same time, and the MVCC mechanism can implement a snapshot view of read operations so that read operations are not affected by other transactions.