TAILIEUCHUNG - Oracle PL/SQL for dummies phần 8

Tham khảo tài liệu 'oracle pl/sql for dummies phần 8', công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | In this part. fter you ve mastered some of the more basic concepts and constructs of PL SQL this part includes a few more advanced topics to enhance your coding knowledge. Chapter 12 discusses the important interactions with the database commits rollbacks locks and so on and how to handle problems that may occur. Chapter 13 shows you how to use SQL and PL SQL dynamically to create very flexible applications where users can select the operations to be executed at runtime. Chapter 14 explains many coding best practices and describes what to do to be a good PL SQL programmer. Chapter 12 Transaction Control Jn This Chapter Handling transactions and data consistency Using commits and rollbacks Performing autonomous transactions transaction is a logical unit of work that comprises a series of SQL data manipulation statements. The COMMIT command permanently saves the changes that all the SQL DML commands data manipulation INSERT UPDATE DELETE made during the current transaction to the database. Conversely a ROLLBACK command ends the transaction and undoes any changes made. This ability to commit a set of database events is one of the cornerstones of a professional relational database. Many smaller PC-based relational database products don t support this concept of a commit and are therefore unsuitable for real-world applications. Problems occur when something unexpected happens. The unexpected event could be the power going out the network being interrupted or even the application raising an unanticipated exception. When this unexpected event occurs execution stops and it is possible that only some of your database changes have been saved. How do you know what went into the database and what didn t How do you get back to a stable point and continue processing Without a COMMIT statement to make the changes made by a set of commands permanent it is almost impossible to recover from unexpected events. In addition to normal transaction processes Oracle has a specialized type

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