MySQL transaction processing: the difference between automatic submission and manual submission

MySQL transaction processing: the difference between automatic submission and manual submission

In the MySQL database, a transaction is a set of SQL statements, either all executed successfully, or all Execution fails, ensuring data consistency and integrity. In MySQL, transactions can be divided into automatic submission and manual submission. The difference lies in the timing of transaction submission and the scope of control over the transaction. The following will introduce the difference between automatic submission and manual submission in detail, and give specific code examples to illustrate.

1. Automatic submission
In MySQL, if transaction processing is not explicitly enabled, each SQL statement will be automatically submitted. In other words, the transaction will be automatically submitted after each SQL statement is executed, and the data modification will take effect immediately, so the consistency of the data cannot be guaranteed.
By default, the auto-commit function is automatically enabled in MySQL. You can control the behavior of automatic submission by setting the autocommit parameter. When autocommit is 1, it means automatic submission is enabled; when autocommit is 0, it means automatic submission is disabled.

The following is a simple code example that demonstrates the behavior of automatic submission:

CREATE TABLE example_table (
    id INT PRIMARY KEY,
    name VARCHAR(50)
);

INSERT INTO example_table VALUES (1, 'Alice');
INSERT INTO example_table VALUES (2, 'Bob');

SELECT * FROM example_table;

After the above code is executed, the data will be automatically submitted, and the data modification will take effect immediately.

2. Manual submission
Manual submission refers to executing multiple SQL statements within a transaction and then manually submitting the transaction at the appropriate time to ensure data consistency. In MySQL, you can use the BEGIN, COMMIT, and ROLLBACK statements to control the commit and rollback of transactions.

The following is a sample code that demonstrates the behavior of manual submission:

SET autocommit = 0; -- Turn off automatic submission

BEGIN; -- Start transaction

UPDATE example_table SET name = 'Alice Smith' WHERE id = 1;
DELETE FROM example_table WHERE id = 2;

SELECT * FROM example_table; -- The data has not yet been submitted and the query results do not contain the latest modifications.

COMMIT; -- Commit the transaction

SELECT * FROM example_table; -- At this time, the data has been submitted, and the query results include the latest modifications

In the above code, manual submission disables automatic submission by setting autocommit to 0, and then uses BEGIN to start the transaction and execute multiple SQL statement, and finally use COMMIT to commit the transaction. During the manual submission process, you can use ROLLBACK at any time to roll back the transaction and undo previous modifications. This ensures data consistency and integrity.

Summary:
Automatic submission and manual submission are two ways of transaction processing in MySQL. The difference lies in the timing and control method of transaction submission. Autocommit automatically commits the transaction after each SQL statement is executed, while manual commit requires explicitly starting and ending the transaction. In actual applications, choose the appropriate submission method as needed to ensure data consistency and integrity.

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