COMMIT and ROLLBACK Statements

COMMIT and ROLLBACK Statements
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COMMIT and ROLLBACK Statements
The ROLLBACK and COMMIT statements are necessary since they update the database when the transaction is successful or not. In particular, the COMMIT statement makes permanent changes in a database when a transaction has taken place successfully. On the contrary, the ROLLBACK statement cancels the changes made by the current transaction in a database and restores the changed data to the state it was before the transaction was initiated.
The COMMIT and ROLLBACK statements relate to one of the database transaction properties, namely consistency. Consistency means that the data in the database remains consistent before and after a transaction (Lotfy, Saleh, El-Ghareeb, & Ali, 2016). Specifically, the COMMIT statement enables a transaction to happen successfully. However, the ROLLBACK statement restores changes made to the database when a transaction fails. Whichever the case, the data remains consistent. For example, if money is transferred from one account to another if the transaction occurs successfully, the total value of finances in the two accounts must be the same at the beginning and end of the transaction.
The four possible concurrency problems are dirty read, unrepeatable read, phantom read, and lost update. A dirty read problem takes place when the uncommitted transaction rolls back later. For example, assume t...