Tham khảo tài liệu 'oracle pl/sql by example- p7', công nghệ thông tin, cơ sở dữ liệu phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | LAB Lab Exercises 272 ROLLBACK SELECT FROM statistics TABLE_NAME TRANSACTIO TRANSACTION_USER TRANSACTI INSTRUCTOR UPDATE STUDENT 09-MAR-08 Notice that even though you roll the UPDATE statement against the INSTRUCTOR table the record is inserted in the STATISTICS table due to the autonomous transaction specified in the trigger body. LAB EXERCISES__ This section provides exercises and suggested answers with discussion related to how those answers most important thing to realize is whether your answer should figure out the implications of the answers and what the effects are of any different answers you may come up with. Understand What a Trigger Is In this exercise you need to determine the trigger firing event its type and so on based on the trigger s CREATE clause. Consider the following CREATE clause CREATE TRIGGER student_au AFTER UPDATE ON STUDENT FOR EACH ROW WHEN NVL Trigger Body. In the WHEN statement of the CREATE clause the pseudorecord OLD allows you to access a row currently being processed. It is important to note that neither NEW nor OLD is prefixed by a colon when it is used in the condition of the WHEN statement. You are already familiar with the pseudorecord OLD pseudorecord allows you to access the current information of the record being updated. In other words it is information currently present in the STUDENT table for a specified NEW pseudorecord allows you to access the new information for the current record. In other words NEW indicates the updated values. For example consider the following UPDATE statement UPDATE student SET zip 01247 WHERE zip 02189 The value 01247 of the ZIP column is a new value and the trigger references it as value 02189 in the ZIP column is the previous value and is referenced as . Please purchase PDF Split-Merge on to remove this watermark. Lab .
