ACID Properties:
Atomicity:
Atomicity means that all the effects of the transaction must complete successfully or the changes are
rolled back. A classic example of an atomic transaction is a withdrawal from an ATM machine; the
machine must both dispense the cash and debit your bank account. Either of those actions completing
independently would cause a problem for either you or the bank.
Consistency:
The consistency requirement ensures that the transaction cannot break the integrity rules of the
database; it must leave the database in a consistent state.
For example:the data i a sex fi eld must be male or female
Isolation:
Isolation refers to keeping the changes of incomplete transactions running at the same time separate
from one another. Each transaction must be entirely self-contained, and changes it makes must not
be readable by any other transaction
Durability:
Once a transaction is committed, it must persist even if there is a system failure — that is, it must be
durable. In SQL Server, the information needed to replay changes made in a transaction is written to
the transaction log before the transaction is considered to be committed.
SQL Server Transactions:
There are two types of transactions in SQL Server that are differentiated only by the way they are
created: implicit and explicit.
Implicit transactions are used automatically by SQL Server to guarantee the ACID properties of
single commands. For example, if you wrote an update statement that modifi ed 10 rows, SQL Server
would run it as an implicit transaction so that the ACID properties would apply, and all 10 rows would
be updated or none of them would.
Explicit transactions are started by using the BEGIN TRANSACTION T-SQL command and are stopped
by using the COMMIT TRANSACTION or ROLLBACK TRANSACTION commands.Committing a transaction effectively means making the changes within the transaction permanent,
whereas rolling back a transaction means undoing all the changes that were made within the transaction.
https://www.youtube.com/watch?v=VLc4ewu6lUI
Atomicity:
Atomicity means that all the effects of the transaction must complete successfully or the changes are
rolled back. A classic example of an atomic transaction is a withdrawal from an ATM machine; the
machine must both dispense the cash and debit your bank account. Either of those actions completing
independently would cause a problem for either you or the bank.
Consistency:
The consistency requirement ensures that the transaction cannot break the integrity rules of the
database; it must leave the database in a consistent state.
For example:the data i a sex fi eld must be male or female
Isolation:
Isolation refers to keeping the changes of incomplete transactions running at the same time separate
from one another. Each transaction must be entirely self-contained, and changes it makes must not
be readable by any other transaction
Durability:
Once a transaction is committed, it must persist even if there is a system failure — that is, it must be
durable. In SQL Server, the information needed to replay changes made in a transaction is written to
the transaction log before the transaction is considered to be committed.
SQL Server Transactions:
There are two types of transactions in SQL Server that are differentiated only by the way they are
created: implicit and explicit.
Implicit transactions are used automatically by SQL Server to guarantee the ACID properties of
single commands. For example, if you wrote an update statement that modifi ed 10 rows, SQL Server
would run it as an implicit transaction so that the ACID properties would apply, and all 10 rows would
be updated or none of them would.
Explicit transactions are started by using the BEGIN TRANSACTION T-SQL command and are stopped
by using the COMMIT TRANSACTION or ROLLBACK TRANSACTION commands.Committing a transaction effectively means making the changes within the transaction permanent,
whereas rolling back a transaction means undoing all the changes that were made within the transaction.
https://www.youtube.com/watch?v=VLc4ewu6lUI
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