SQL Server transactions

A transaction is a mechanism and an operation sequence. It contains a group of database operation commands. All the commands will be used as a whole, and they will be submitted or revoked together to the system. The requests will either be executed or not executed.

Therefore, a transaction is an inseparable logical unit of work, similar to the concept of the operating system. When performing concurrent operations on the database system, transactions are used as the smallest control unit.

In SQL, statements that define transaction operations,

Begin transaction

Commit transaction

Rollback transaction

 

Features of transactions:

Atomicity, consistency, isolation, and durability.

 

The following example shows the application of transaction rollback:

Begin transaction my_transaction_delete

Use company -- Use Database

Go

Delete from department where dept_id = '123' -- delete

Save transaction after_delete -- set the transaction recovery point

 

Update employee set dept_id = '20160301' where dept_id = '20160301'

-- The employee ID of the logistics department is changed to the manager's office ID

If @ error <> 0 Ro @ rowcount = 0 then

-- Check whether the update is successful. @ error returns the status of an SQL statement. If the value is not zero, an error is returned. If the value is not zero, an error is returned. If the value is incorrect, a rollback occurs.

Begin

Rollback Tran after_delete -- roll back to the storage point

Commit tran -- if no error occurs, data can be submitted.

Print 'updating employee information is generating an error'

Return

End

 

Commit transaction my_transaction_delete

Go