Расскажите про уровни изоляции транзакций: Read Uncommitted, Read Committed, Repeatable Read, Serializable.

Transaction isolation levels determine how and when the changes made by one transaction become visible to other transactions, as well as what anomalies may occur during concurrent execution.

• Read Uncommitted — the lowest level of isolation. Transactions can see uncommitted changes of other transactions (dirty reads). All types of anomalies are possible.

• Read Committed — a transaction only sees changes that have been committed. Dirty reads are prevented, but non-repeatable reads can occur, where repeated reads of the same data may yield different results.

• Repeatable Read — guarantees that data read in a transaction will not change until it completes. It prevents non-repeatable reads but allows phantom reads (the appearance of new rows upon re-query).

• Serializable — the strictest level. Transactions are executed as if they were sequential, one after another. It prevents all types of anomalies, including phantom reads, but may reduce concurrency and performance.

In Go, when working with databases, these levels can be set via drivers or ORM, for example, using SQL queries like SET TRANSACTION ISOLATION LEVEL ... at the beginning of a transaction.