DISPARADORES ORACLE PDF

That way, you can create triggers just not row triggers to read and modify the parent and child tables. More than one trigger can disparadroes created didparadores an object. If a view contains pseudocolumns or expressions, then you can only update the view with an UPDATE statement that does not refer to any of the pseudocolumns disparadorees expressions. You might use the AFTER keyword if you want the trigger to query or change the same table, because triggers can only do that after the initial changes are applied and the table is back in a consistent state. For example, to disable all triggers defined for the Inventory table, enter the following statement: You cannot define your own event conditions.

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Triggers on System Events and User Events Row Triggers and Statement Triggers When you define a trigger, you can specify the number of times the trigger action is to be run: Once for every row affected by the triggering statement, such as a trigger fired by an UPDATE statement that updates many rows Once for the triggering statement, no matter how many rows it affects Row Triggers A row trigger is fired each time the table is affected by the triggering statement.

If a triggering statement affects no rows, a row trigger is not run. Row triggers are useful if the code in the trigger action depends on data provided by the triggering statement or rows that are affected.

For example, Figure illustrates a row trigger that uses the values of each row affected by the triggering statement. Statement Triggers A statement trigger is fired once on behalf of the triggering statement, regardless of the number of rows in the table that the triggering statement affects, even if no rows are affected.

Statement triggers are useful if the code in the trigger action does not depend on the data provided by the triggering statement or the rows affected. For example, use a statement trigger to: Make a complex security check on the current time or user Generate a single audit record BEFORE and AFTER Triggers When defining a trigger, you can specify the trigger timing—whether the trigger action is to be run before or after the triggering statement.

This type of trigger is commonly used in the following situations: When the trigger action determines whether the triggering statement should be allowed to complete. Using a BEFORE trigger for this purpose, you can eliminate unnecessary processing of the triggering statement and its eventual rollback in cases where an exception is raised in the trigger action.

Trigger Type Combinations Using the options listed previously, you can create four types of row and statement triggers: BEFORE statement trigger Before executing the triggering statement, the trigger action is run. BEFORE row trigger Before modifying each row affected by the triggering statement and before checking appropriate integrity constraints, the trigger action is run, if the trigger restriction was not violated.

AFTER statement trigger After executing the triggering statement and applying any deferred integrity constraints, the trigger action is run.

AFTER row trigger After modifying each row affected by the triggering statement and possibly applying appropriate integrity constraints, the trigger action is run for the current row provided the trigger restriction was not violated. You can have multiple triggers of the same type for the same statement for any given table.

Multiple triggers of the same type permit modular installation of applications that have triggers on the same tables. Modify Views Modifying views can have ambiguous results: Deleting a row in a view could either mean deleting it from the base table or updating some values so that it is no longer selected by the view. Inserting a row in a view could either mean inserting a new row into the base table or updating an existing row so that it is projected by the view.

Updating a column in a view that involves joins might change the semantics of other columns that are not projected by the view. Object views present additional problems. This operation inevitably involves joins, but modifying joins is inherently ambiguous. As a result of these ambiguities, there are many restrictions on which views are modifiable.

A view is inherently modifiable if data can be inserted, updated, or deleted without using INSTEAD OF triggers and if it conforms to the restrictions listed as follows. Even if the view is inherently modifiable, you might want to perform validations on the values being inserted, updated or deleted. Here the trigger code performs the validation on the rows being modified and if valid, propagate the changes to the underlying tables. To modify an object materialized by an object view in the client-side object cache and flush it back to the persistent store, you must specify INSTEAD OF triggers, unless the object view is inherently modifiable.

However, it is not necessary to define these triggers for just pinning and reading the view object in the object cache. See Also:.

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- Disparador (trigger)

Triggers on System Events and User Events Row Triggers and Statement Triggers When you define a trigger, you can specify the number of times the trigger action is to be run: Once for every row affected by the triggering statement, such as a trigger fired by an UPDATE statement that updates many rows Once for the triggering statement, no matter how many rows it affects Row Triggers A row trigger is fired each time the table is affected by the triggering statement. If a triggering statement affects no rows, a row trigger is not run. Row triggers are useful if the code in the trigger action depends on data provided by the triggering statement or rows that are affected. For example, Figure illustrates a row trigger that uses the values of each row affected by the triggering statement. Statement Triggers A statement trigger is fired once on behalf of the triggering statement, regardless of the number of rows in the table that the triggering statement affects, even if no rows are affected. Statement triggers are useful if the code in the trigger action does not depend on the data provided by the triggering statement or the rows affected.

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DISPARADORES ORACLE PDF

Use this clause to change the definition of an existing trigger without first dropping it. If you omit schema, then Oracle Database creates the trigger in your own schema. If a trigger produces compilation errors, then it is still created, but it fails on execution. This means it effectively blocks all triggering DML statements until it is disabled, replaced by a version without compilation errors, or dropped.

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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. 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.

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