What behavior is expected when reading data that has not yet been committed?

When reading data that has not yet been committed (i.e., is in an uncommitted transaction state), the behavior depends on the transaction isolation level in the database and the technology used.

In most cases, if a transaction is not committed, other transactions will not see these changes — this is called "read committed" or more strict isolation levels. Therefore, reading uncommitted data is usually impossible or will result in reading old values.

If the "read uncommitted" isolation level is used, then "dirty" reads are possible, meaning data that might be rolled back.

In Java, when working with databases via JDBC or ORM (e.g., Hibernate), the behavior of reading uncommitted data is controlled by transaction settings and the isolation level. For example:

connection.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);

Ultimately, without explicitly setting the "read uncommitted" isolation level, reading uncommitted data does not occur.