MySQL Implicit Commits

How it works

Many schema statements cause implicit commits in MySQL. Atomic DDL means the DDL operation itself has an atomic implementation; it does not mean the statement behaves like ordinary transactional DML that a caller can freely roll back. This isolated lab updates a quantity, creates a normal table and then issues ROLLBACK. The final quantity shows why a migration must not rely on a surrounding transaction as a universal undo plan.

Run in a disposable MySQL lab

Use Oracle MySQL 8.4 with InnoDB, not Bhylu’s SQLite playground. The examples were reviewed on MySQL 8.4.8. XAMPP may provide MariaDB, which has different feature and collation behaviour. Check your actual server before running the script. These lessons do not require a change to Bhylu’s PHP, Apache or normal database service.

1. On a separate lab instance, create the empty bhylu_mysql_lab schema. Stop if it already exists; do not overwrite an existing database.
2. Select that schema and import the complete repair-parts seed once. It sets the documented session mode, utf8mb4 collation, UTC and English date-name locale.
3. Run this lesson in a fresh copy of the seed, not after another lesson’s writes. Use the command-line client or a compatible editor. DELIMITER lines are client instructions for stored-program examples.

Download this complete lesson script. Its setup is the linked seed; review the dataset before changing it. Administrative and destructive examples are restricted to the specifically named disposable objects. Every script repeats the session settings because each new connection has its own session. No MySQL browser runner is currently available.

Example

SET NAMES utf8mb4 COLLATE utf8mb4_0900_ai_ci;
SET SESSION sql_mode = 'STRICT_TRANS_TABLES,ONLY_FULL_GROUP_BY,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
SET SESSION time_zone = '+00:00';
SET SESSION lc_time_names = 'en_US';
START TRANSACTION;
UPDATE parts SET quantity = 9 WHERE id = 1;
CREATE TABLE ddl_marker (id INT PRIMARY KEY) ENGINE=InnoDB;
ROLLBACK;
SELECT quantity FROM parts WHERE id = 1;

Expected result

9

The update survives because the CREATE TABLE establishes an implicit transaction boundary. Temporary-table statements have different rules, but they are not a general escape from migration design either. Read the exact statement’s documentation and review backups, compatibility and recovery procedures. This example runs only in a fresh disposable schema, never against a real stock table.