About
Dirty reads is a phenomena (data problem) that occurs when a transaction reads uncommitted data in another transaction.
Dirty read can not provide read consistency.
Dirty reads
- compromise data integrity,
- violate foreign keys,
- and ignore unique constraints.
Example
To illustrate a problem with dirty reads, suppose:
- one transaction updates a column value without committing.
- a second transaction reads the updated and dirty (uncommitted) value.
- the first session rolls back the transaction so that the column has its old value,
- but the second transaction proceeds using the updated value, corrupting the database.