Chapter 10, Problem 17RQ

Program Plan Intro

ANSI transaction isolation level:

Transaction isolation levels indicate the degree of the transaction which specifies protected or isolated transactions from other concurrent transactions. The ANSI SQL standard defines transaction management based on transaction isolation levels.

The isolation level is specified based on type of read that allows in the transaction. The type of read operation is divided into three types.

• Dirty read
• Non-repeatable read
• Phantom read

Dirty read:

• The transaction can read the data before it goes to the committed state is known as dirty read.

Non-repeatable read:

• If the transaction read an attribute at time “t1”, and then the transaction reads the same attribute at time “t2” prints different results.
• The original attribute can change their data.

Phantom read:

• It returns additional rows when the transaction executes a query at different time to satisfy the query.