The degree to which concurrent transactions can affect one another.
A level that defines how much of another transaction's uncommitted changes are visible between concurrently running transactions, with several stages such as READ COMMITTED. Each level tolerates a different set of anomalies: READ UNCOMMITTED allows a dirty read, where you can see another transaction's uncommitted changes, while even REPEATABLE READ can still allow a phantom read, where re-running the same query surfaces rows that were newly inserted in between.
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