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You will also learn about different characters of triggers and their usage in the database. The event can be any of the following:. The act of executing a trigger is also known as firing a trigger. We say that the trigger is fired.

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A trigger can have the same name as another kind of object in the schema for example, a table ; however, Oracle recommends using a naming convention that avoids confusion.

By default, a trigger is created in the enabled state. You can disable an enabled trigger, and enable a disabled trigger. Unlike a subprogram, a trigger cannot be invoked directly. A trigger is invoked only by its triggering event, which can be caused by any user or application.

You might be unaware that a trigger is executing unless it causes an error that is not handled properly. A simple trigger can fire at exactly one of these timing points :. A compound trigger can fire at multiple timing points. A system trigger is defined on a schema or the database. A trigger defined on a schema fires for each event associated with the owner of the schema the current user. A trigger defined on a database fires for each event associated with all users.

One use of triggers is to enforce business rules that apply to all client applications. A trigger on the table can ensure the proper format of all data added to it. Because the trigger executes whenever any client adds data to the table, no client can circumvent the rules, and the code that enforces the rules can be stored and maintained only in the trigger, rather than in every client application. This section shows how to use both of these ways to create triggers.

They are called pseudorecords because they have some, but not all, of the properties of records. However, these primary keys are not inserted into the table automatically. Oracle Database compiles the procedure and saves it. A view presents the output of a query as a table. Instead of changing the view, they change the underlying tables.

OLD and NEW store the original and new values, respectively, of the record being processed by the trigger. In the frame to the right of the Connections frame, the Code pane appears, showing the code that created the trigger. The Code pane is in write mode.

Clicking the pencil icon switches the mode from write mode to read only, or the reverse. The title of the pane is in italic font, indicating that the change is not yet saved in the database. Oracle Database compiles the trigger and saves it. The title of the pane is no longer in italic font.

You might need to temporarily disable triggers if they reference objects that are unavailable, or if you must upload a large amount of data without the delay that triggers cause as in a recovery operation. After the referenced objects become available, or you have finished uploading the data, you can re-enable the triggers. In the list of choices, select Disable or Enable.

For example, these statements disable and enable all triggers on the evaluations table:. In the list of choices, select Disable All or Enable All. To see the compilation errors, use this statement:. Compiled triggers depend on the schema objects on which they are defined. If an object on which a trigger depends is dropped, or changed such that there is a mismatch between the trigger and the object, then the trigger is invalidated. The next time the trigger is invoked, it is recompiled.

For example:. Note: To create triggers, you must have appropriate privileges; however, for this discussion, you do not need this additional information. In the list of schema object types, right-click Triggers. In the list of choices, click New Trigger. Deselect the option Statement Level. Click OK. In the list of schema object types, expand Triggers. In the list of triggers, click the trigger to change.

In the Code pane, change the code. From the File menu, select Save. Disabling and Enabling Triggers You might need to temporarily disable triggers if they reference objects that are unavailable, or if you must upload a large amount of data without the delay that triggers cause as in a recovery operation.

In the list of triggers, right-click the desired trigger. In the Disable or Enable window, click Apply. In the Confirmation window, click OK.

In the list of schema object types, expand Tables. In the list of tables, right-click the desired table. In the list of choices, select Triggers. Dropping Triggers You must drop a trigger before dropping the objects on which it depends. In the list of triggers, right-click the name of the trigger to drop.

In the list of choices, click Drop Trigger. In the Drop window, click Apply.

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Oracle Trigger

A trigger can have the same name as another kind of object in the schema for example, a table ; however, Oracle recommends using a naming convention that avoids confusion. By default, a trigger is created in the enabled state. You can disable an enabled trigger, and enable a disabled trigger. Unlike a subprogram, a trigger cannot be invoked directly. A trigger is invoked only by its triggering event, which can be caused by any user or application. You might be unaware that a trigger is executing unless it causes an error that is not handled properly.

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A trigger is like a stored procedure that Oracle Database invokes automatically whenever a specified event occurs. Unlike a stored procedure, you can enable and disable a trigger, but you cannot explicitly invoke it. While a trigger is enabled , the database automatically invokes it—that is, the trigger fires —whenever its triggering event occurs. While a trigger is disabled , it does not fire. You specify the triggering event in terms of triggering statements and the item on which they act.

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