Final answer:
Transaction initiation occurs implicitly when SQL operations like INSERT, UPDATE, or DELETE are executed, or explicitly when the BEGIN TRANSACTION statement is used. This maintains database integrity by treating multiple operations as an atomic unit and adhering to the ACID properties.
Step-by-step explanation:
Transaction initiation is done implicitly or explicitly when particular SQL statements are encountered. In SQL, transactions are important for maintaining database integrity and are used to execute a sequence of operations as a single unit. A transaction is often initiated implicitly when a statement is executed that cannot run outside of a transaction, such as INSERT, UPDATE, or DELETE. However, a transaction can also be started explicitly by using the BEGIN TRANSACTION statement. The explicit initiation gives you control over when the transaction starts and includes multiple operations that should be treated as a single atomic unit. To ensure data consistency, transactions follow the ACID properties, which stands for Atomicity, Consistency, Isolation, and Durability. A transaction will either complete in its entirety or have no effect at all if anything goes wrong (Atomicity). It will not violate any database constraints (Consistency), is executed independently of other transactions (Isolation), and once committed, the changes are permanent (Durability). In database management systems, transactions can be initiated explicitly by the programmer using keywords like BEGIN TRANSACTION or START TRANSACTION. However, transactions can also be initiated implicitly by the system when certain SQL statements that require a transaction are encountered. For example, many systems automatically start a transaction when an INSERT, UPDATE, DELETE, or similar data-modifying SQL statement is executed. Implicit initiation ensures that a series of related operations are treated as a single unit, providing the benefits of atomicity, consistency, isolation, and durability (ACID properties).