What are the different levels of transaction isolation in SQL?

What are the different levels of transaction isolation in SQL?

In SQL, there are four main levels of transaction isolation: Read Uncommitted, Read Committed, Repeatable Read, and Serializable.

Can you explain each level with examples?

Sure!

1. Read Uncommitted: Allows dirty reads. For example, if Transaction A updates a row but hasn't committed, Transaction B can read that uncommitted data.
2. Read Committed: Prevents dirty reads. Transaction B can only read committed data from Transaction A.
3. Repeatable Read: Ensures that if Transaction B reads a row, it will see the same data if it reads it again, even if Transaction A modifies it in between.
4. Serializable: The strictest level, it ensures complete isolation from other transactions, making it appear as if transactions are executed one after another.

What are the trade-offs of using higher isolation levels?

Higher isolation levels can lead to increased data integrity but may also result in reduced concurrency and performance due to locking and blocking.