MySql locks and transactions: a complete MySQL database transaction execution process

MySQL is a commonly used relational database that is widely used in enterprise-level applications. In order to ensure the integrity and consistency of data, MySQL provides a variety of lock and transaction mechanisms. In this article, we will delve into the concepts related to MySQL locks and transactions, as well as the complete process of MySQL database transaction execution.

The concept of MySQL lock

Lock is a mechanism to control concurrent access to the database. When multiple users access the same database at the same time, without a locking mechanism, data may be lost, damaged, or inconsistent. MySQL provides two commonly used lock mechanisms: shared locks and exclusive locks.

Shared Lock: Multiple users can request shared locks at the same time for reading data. Shared locks do not prevent other users from obtaining shared locks, but they do prevent other users from obtaining exclusive locks.

Exclusive Lock: Only one user can obtain an exclusive lock for writing or modifying data. An exclusive lock prevents other users from acquiring shared or exclusive locks.

The concept of MySQL transaction

In MySQL, a transaction can be regarded as a set of related SQL statements. These statements are either all executed successfully, or all are rolled back to the original state. MySQL transactions have four characteristics:

Atomicity: MySQL transactions are atomic, that is, all operations in the transaction are either successfully executed or rolled back to the original state.

Consistency: MySQL transactions ensure data consistency, that is, the database must remain consistent before and after the transaction is executed.

Isolation: MySQL transactions are isolated, that is, transactions are isolated from each other during concurrent access, and each transaction accesses data seemingly independently.

Durability (Durability): MySQL transactions guarantee the durability of data, that is, after the transaction is submitted, modifications to the database must be permanently saved.

The complete process of MySQL database transaction execution

In MySQL, a complete transaction execution process includes the following four steps:

1. Start transaction

When you need to execute a database transaction, you first need to use the BEGIN or START TRANSACTION command to start a new transaction. At the beginning of a transaction, MySQL automatically acquires an exclusive lock to prevent other users from modifying the data of the current transaction.

2. Execute SQL statements

During transaction execution, a series of SQL statements need to be executed. These SQL statements can read, write or modify data. During the execution of SQL statements, the corresponding lock mechanism needs to be implemented based on business logic to ensure data integrity and consistency.

3. Commit or rollback the transaction

After all SQL statements in the transaction have been executed, you need to use the COMMIT command to submit the transaction to the database. If the transaction is executed successfully and submitted, MySQL will release the exclusive lock, allowing other users to modify the data. If transaction execution fails, you need to use the ROLLBACK command to roll back the transaction to the original state.

4. End transaction

At the end of the transaction, you need to use the END or COMMIT command to end the current transaction. After ending the transaction, MySQL will release all locks to allow other users to access and modify the database.

Conclusion

MySQL provides a variety of lock and transaction mechanisms to ensure data integrity and consistency. For databases that require concurrent modifications, it is necessary to use the MySQL lock and transaction mechanism. In actual development, it is necessary to combine business requirements and database characteristics and adopt appropriate lock and transaction mechanisms to achieve efficient and stable database access.

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