One of the essential features of SQLite is its support for transaction processing, which ensures data consistency and reliability.
A transaction in SQLite is a series of database operations that are performed as a single unit of work. Transactions are used to ensure that a set of related database operations either complete successfully or are rolled back if any errors occur, ensuring data integrity.
When a transaction is started in SQLite, it acquires a transactional lock on the database, which prevents other transactions from modifying the same data until the first transaction is either committed or rolled back. Once the transaction is committed, the transactional lock is released, and the changes made during the transaction are saved permanently to the database.
The COMMIT statement in SQLite is used to save the changes made during a transaction. When the COMMIT statement is executed, SQLite releases the transactional lock on the database and writes the changes made during the transaction to disk. Once the changes have been saved to disk, they are considered permanent and can be accessed by other transactions.
It’s essential to note that if an error occurs during the transaction, the changes made before the error will not be saved, and the transaction will be rolled back. In this case, the transactional lock will be released, and the database will return to its previous state, undoing any changes made during the failed transaction.
Example
Suppose we have a table called “employees” with the following fields: “id”, “name”, “age”, “position”, and “salary”. We want to insert a new employee into the table and commit the transaction:
BEGIN TRANSACTION;
INSERT INTO employees (name, age, position, salary)
VALUES ('John Doe', 30, 'Manager', 50000);
COMMIT;
In this example, we first begin a transaction with the BEGIN TRANSACTION statement. Then, we insert a new employee with the INSERT INTO statement, specifying the values for the name, age, position, and salary fields. Finally, we commit the transaction with the COMMIT statement, which saves the changes to the database.
In conclusion, the COMMIT statement in SQLite is a crucial feature that ensures data consistency and reliability in a transactional database environment. It allows developers to save changes made during a transaction and release the transactional lock, making the data available for other transactions.
