The definition and characteristics of MySQL transactions

The definition and characteristics of MySQL transactions

MySQL is an open source relational database management system. Transactions are a very important concept in database management systems. A transaction refers to the execution of a set of SQL statements. These SQL statements are either all executed or none of them are executed to ensure the integrity and consistency of the data. Transactions have four ACID characteristics, namely atomicity, consistency, isolation and durability.

1. Atomicity: All operations in a transaction are either successfully executed or rolled back after failure. There will be no situation where some operations succeed and some fail.
2. Consistency: The database must be in a consistent state before the transaction is executed, and the database remains consistent after the transaction is executed.
3. Isolation: Multiple transactions are isolated from each other, and the execution of one transaction is not interfered with by other transactions.
4. Durability (Durability): Once a transaction is committed, the modifications made will be permanently saved in the database, and the durability of the data can be guaranteed even if the database fails.

The following is a specific code example to demonstrate the characteristics of MySQL transactions:

-- 创建一个测试表
CREATE TABLE student (
    id INT PRIMARY KEY,
    name VARCHAR(50),
    age INT
);

-- 开启事务
START TRANSACTION;

-- 插入数据
INSERT INTO student VALUES (1, 'Alice', 20);

-- 查询数据
SELECT * FROM student;

-- 提交事务
COMMIT;

In the above example, we first created a table named student, and then opened a affairs. Then a piece of data was inserted into the table, and then the data was queried. Finally, the transaction is submitted through the COMMIT statement, making the data insertion operation effective.

If you encounter an error or need to roll back the transaction, you can use the ROLLBACK statement to roll back the transaction. The example is as follows:

-- 开启事务
START TRANSACTION;

-- 插入数据
INSERT INTO student VALUES (2, 'Bob', 25);

-- 查询数据
SELECT * FROM student;

-- 回滚事务
ROLLBACK;

In this example, if an error occurs after inserting data or If you need to give up this operation, you can roll back the transaction through the ROLLBACK statement, undo the previous operation, and maintain the consistency of the database.

Through the above examples, we can see the characteristics of MySQL transactions and how to open, commit and rollback transactions in MySQL. Transactions can ensure the consistency and stability of the database and are a very important concept in database management systems.

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