Why are isolation levels necessary in database transactions?

In database transactions, isolation levels are used to control the visibility of changes made by one transaction to others. They help manage issues such as:

• Dirty read: reading uncommitted data from another transaction.
• Non-repeatable read: data changes between two reads within the same transaction.
• Phantom read: new rows appear in the result of a repeated query.

Different isolation levels (e.g., Read Uncommitted, Read Committed, Repeatable Read, Serializable) balance performance and strict data consistency, allowing you to choose the appropriate level of protection based on application requirements.