Several SQL operations are performed by User 1 to access the Fee information for Bowling in the Act_Fee relation (shown in the exhibit). The first access returns a fee of 50. An unrelated SQL operation by another user updates the Bowling fee to 60. The second access by User 1 returns a fee of 60. What problem has occurred?
The problem that has occurred is a dirty read. A dirty read refers to a situation where one transaction reads data from a database that has been modified by another ongoing transaction but has not yet been committed. In this case, the first access by User 1 returns a fee of 50 for Bowling. Then, another user performs an update operation changing the Bowling fee to 60. When User 1 accesses the fee information again, the new value of 60 is read. This indicates that User 1's second read has been influenced by an uncommitted change from another transaction, leading to a dirty read scenario.
a dirty read refers to a situation where one transaction reads data from a database that has been modified by another ongoing transaction but has not yet been committed or rolled back. This phenomenon occurs in concurrent database operations, where multiple transactions can access and modify the same data simultaneously. The sequence of events in a dirty read scenario is as follows: Transaction A reads a value from a data item in the database. Transaction B updates the same data item but has not committed the changes yet. Transaction A reads the modified value (dirty data) before Transaction B has finished and committed its changes. The problem with dirty reads is that Transaction A may obtain and act upon inaccurate or inconsistent data, which may lead to incorrect results or decisions. Dirty reads can cause data integrity issues and are generally considered undesirable in a database system.