Read Uncommitted
Read uncommitted is the lowest isolation level, allowing dirty reads: a transaction can see other transactions uncommitted modifications.
Purpose
To understand the risks of the lowest isolation level; use only when consistency requirements are minimal to maximize concurrency.
Mechanism
Reads take no locks and can see rows other transactions are modifying but have not committed (dirty data). If that transaction rolls back, the reader saw data that never existed. Rarely used.
Use cases
- Isolation level comparison
- Maximizing concurrency
- Dirty read risk analysis