SQL Interview Questions and answers on Database Transactions

SQL Interview Questions and answers on Database Transactions

1)What is a database transaction?

Database transaction take database from one consistent state to another. At the end of the transaction the system must be in the prior state if transaction fails or the status of the system should reflect the successful completion if the transaction goes through.

2) What are properties of a transaction? 

Properties of the transaction can be summarized as ACID Properties.

1. Atomicity

A transaction consists of many steps. When all the steps in a transaction gets completed, it will get reflected in DB or if any step fails, all the transactions are rolled back.

2. Consistency

The database will move from one consistent state to another, if the transaction succeeds and remain in the original state, if the transaction fails.

3. Isolation

Every transaction should operate as if it is the only transaction in the system

4. Durability

Once a transaction has completed successfully, the updated rows/records must be available for all other transactions on a permanent basis