Database Errors

Jun 21, 2023

A transaction reads data written by a concurrent uncommitted transaction.
Since it is uncommitted it may rollback (and leave to a wrong data being read), leading to a dirty read.

A transaction re-reads data it has previously read and finds that data has been modified by another transaction (that committed since the initial read).
Leading to a unmatched record.

A transaction re-executes a query returning a set of rows that satisfy a search condition and finds that the set of rows satisfying the condition has changed due to another recently-committed transaction.

The result of successfully committing a group of transactions is inconsistent with all possible orderings of running those transactions one at a time.