Description: Read consistency is a fundamental concept in SQL query optimization that refers to the ability to ensure that a read operation returns a coherent and stable view of the data, even in situations where multiple transactions are occurring concurrently. This is crucial in database environments where updates and reads can happen simultaneously, as without proper control, a query could return inconsistent or erroneous results. Read consistency is achieved through different transaction isolation levels, which determine how and when changes made by one transaction are visible to others. For example, in a ‘Read Committed’ isolation level, a transaction can only read data that has been committed, thus avoiding reading intermediate data that could be rolled back. This approach not only enhances data integrity but also optimizes query performance by reducing the likelihood of unnecessary locks and waits. In summary, read consistency is essential to ensure that applications relying on databases can operate reliably and efficiently, providing users with accurate and up-to-date results.
