SQL Server- ACID properties of Transactions

Hello friends, today we are going to learn about ACID properties of transactions. Let’s try first, to understand what is a transaction?

Transaction:-A transaction is a batch of SQL statements that behaves like a single unit. In simple words, a transaction is a unit where a sequence of work is done to complete the whole activity. We can take an example of Bank transaction to understand this.

When we transfer money from account “A” to account “B”, a transaction takes place. We can refer below image to understand the transaction. There are two sequence of work in amount transfer, one is debiting account “A” and second is crediting account “B”. I hope now you got my point.

Every transaction has four characteristics, those are known as ACID properties.

•          Atomicity
•          Consistency
•          Isolation
•          Durability

Atomicity: - Every transaction follow atomicity model, which means that if a transaction is started, it should be either completed or rollback. To understand this lets take above example, if person is transferring amount from account “A” to account “B”, it should be credited to account B after completing the transaction. In case if any failure happens, after debiting amount from account “A” , the change should be rollback.

Consistency: - Consistency says that after the completion of a transaction, changes made during the transaction should be consistent. Let’s understand this fact by referring the above example, if account “A” has been debited by 200 RS then after completion of transaction account “B” should be credited by 200 RS. It means changes should be consistent.

Isolation: - Isolation states that every transaction should be isolated with each other, there should not be any interference between two transactions.

Durability: - Durability means that once the transaction is completed, all the changes should be permanent, it means that in case of any system failure, changes should not be lost.