Database Abstraction Layer and Transaction in Stored procedures
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Transcript of Database Abstraction Layer and Transaction in Stored procedures
Disclaimer: This presentation is prepared by trainees of baabtra as a part of mentoring program. This is not official document of baabtra –Mentoring PartnerBaabtra-Mentoring Partner is the mentoring division of baabte System Technologies Pvt . Ltd
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Database Access Layer Module &
Database Transaction
[email protected]/usernametwitter.com/usernamein.linkedin.com/in/profilenamePhonenumber
Data Access Layer
• A data access layer follows the idea of "separation of concerns“.
• DAL consist of the code used to pull data from a db.
• Its isolated from business logic layer and presentation layer.
mamanages database
Why???? DAL
• DAL allow us to change more easily the backend physical data storage technology without having large impact on business logic layer.
• Data access layers allow us to access data the same way for different application in our program.
DB Transaction
• A transaction is a discrete unit of work that must be completely processed or not processed at all.
Transaction states• Active, the initial state; the transaction stays
in this state until while it is still executing.
• A transition is terminated only if it has either been committed or aborted.
Transaction States
• Partially committed, After the final statement has been executed
• At this point failure is still possible since changes may have been only done in main memory, a hardware failure could still occur.
Transaction States
• Committed- after successful completion.• Once committed, the transaction can no
longer be undone by aborting it. • Its effect could be undone only by a
compensating transaction.
Transaction States
• Failed, after the discovery that normal execution can no longer proceed.
• Once a transaction can not be completed, any changes that it made must be undone rolling it back.
Transaction States
• Aborted, after the transaction has been rolled back the database has been restored to its state prior to the start of the transaction.
• The DBMS could either kill the transaction or restart the transaction.
Create procedure DeleteDepartment ( @DepartmentID int ) AS BEGIN TRANSACTION DELETE FROM Employees WHERE DepartmentID = @DepartmentIDIF @@ERROR <> 0 BEGIN ROLLBACK RAISERROR ('Error in deleting employees in DeleteDepartment.', 16, 1) RETURN END DELETE FROM Departments WHERE DepartmentID = @DepartmentID IF @@ERROR <> 0 BEGIN ROLLBACK RAISERROR ('Error in deleting department in DeleteDepartment.', 16, 1) RETURN END COMMIT
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