A transaction is a logical unit of work that contains one or more SQL statements.
Transactions are atomic units of work that can be committed or rolled back. When a transaction makes multiple changes to the database, either all the changes succeed when the transaction is committed, or all the changes are undone when the transaction is rolled back.
A transaction begins with the first executable SQL statement. A transaction ends when it is committed or rolled back, either explicitly with a COMMIT or ROLLBACK statement or implicitly when a DDL (Data Definition Language (DDL) is used to manage table and index structure and CREATE, ALTER, RENAME, DROP and TRUNCATE statements are to name a few data definition elements) statement is issued.