MySQL is a relational database — it stores data in tables with rows and columns. Schema is fixed — every record must follow the same structure. It is good for structured data with relationships — like users, orders, products tables connected with foreign keys. I use MySQL for applications like banking or finance where data structure never changes.
Transactions group multiple operations as atomic units. All or nothing execution (ACID compliance). Commands: START TRANSACTION, COMMIT (save), ROLLBACK (undo). Use for operations that must succeed together (money transfer). Prevents inconsistent states. Set isolation levels: READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE.