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Database Administrator’s Guide. Contents. Previous Next. Page of Search. This Book This Release. Table of Contents. open Oracle Database. Overview of Triggers. A trigger is a named program unit that is stored in the database and fired (executed) in response to a specified event. The specified event. Prerequisites. The trigger must be in your own schema or you must have ALTER ANY TRIGGER system privilege. In addition, to alter a trigger on DATABASE.

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When the trigger fires, the declarative part executes before any timing-point sections execute. Triggers can also require the user to supply a “reason code” for issuing the audited SQL statement, which can be useful in both row and statement-level auditing situations.

However, unless autonomous transactions are used, any audit information generated by a trigger is rolled back if the triggering statement is rolled back.

The row correlation variables inside the trigger correspond to the nested table element. Oracle Database fires such a trigger whenever a DML statement affects the table. They are executed for every user every time the event occurs on which the trigger is created.

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 or expressions. Guidelines for Designing Triggers Use the following guidelines when designing triggers: Each trigger can see the old and new values. By default, triggers are enabled when first created. For example, if you execute the following SQL statement: When this trigger is created, Oracle Database enables it automatically.

Disabling Triggers Consider temporarily disabling a trigger if one of the following conditions is true: Standard auditing options permit auditing of DML and DDL statements regarding all types of schema objects and structures. Triggers associated with startup and shutdown events must be defined on the database instance.

Only use triggers to enforce complex security authorizations that cannot be defined using the database security features provided with Oracle Database. If you omit schemathen Oracle Database creates the trigger in your own schema.

Oracle / PLSQL: AFTER INSERT Trigger

For example, disparsdores can use triggers to: In particular, if an uncommitted transaction has modified values that a trigger being fired either must read query or write updatethen the SQL statements in the body of the trigger being fired use the following guidelines: You might omit this clause if you just want to record the fact that the operation occurred, but not examine the data for each row.


Therefore, do not create triggers that depend on the order in which rows are processed. The order in which Oracle Database fires these triggers is indeterminate.

That way, you can create triggers just not row triggers to read and modify the parent and child tables. The statement level triggers are useful for performing validation checks for the entire statement.

Also, this trigger does not allow triggers to cycle such as, A fires B fires A. Triggers can enforce integrity rules other than referential integrity.

Triggers are commonly used to enforce complex security authorizations for table data. The OR REPLACE option is provided to allow a new version of an existing trigger to replace the older version, without affecting any grants made for the original version of the trigger. Error Conditions and Exceptions in the Trigger Body If a predefined or user-defined error condition exception is raised during the execution of a trigger body, then all effects of the trigger body, as well as the triggering statement, are rolled back unless the error is trapped by an exception handler.

They are provided to assist you in designing your own triggers. Specify the schema and table or view name of one of the following on which the trigger is to be created:.

Enabling and Disabling Triggers

For example, to enable the disabled trigger named Reorderdisparadorss the following statement: The fisparadores of the data in p and f is lost. From there, your application can control how much access this user disparadires, based on his or her session information. If you have multiple triggers of the same type on the same table, and the order in which they execute is important, use the FOLLOWS clause.

If the triggering statement of a compound trigger is an INSERT statement that includes a subquery, the compound trigger retains some of its performance benefit. The following example illustrates how a roacle can be used to derive new column values for a table whenever a row is inserted or updated. The mutating error described in Trigger Restrictions on Mutating Tables prevents the trigger from reading or modifying the table that the parent statement is modifying.


For example, assume a trigger is defined as the following:. You are loading data into the table to which the trigger applies.

They are executed for every user every time the event occurs on fisparadores the trigger is created. You might use the AFTER keyword if you want the trigger to query or change the same table, because triggers can only do that disapradores the initial changes are applied and the table is back in a consistent state. For example, the following statement shows the dependencies oracl the triggers in the HR schema:. However, the AFTER row trigger fires once for each row of the table affected by the triggering statement, while the AFTER statement trigger fires only once after the triggering statement execution is completed.

For callouts, these are passed as IN arguments. The following statement, inside a disparwdores, returns the owner of the trigger, not the name of user who is updating the table:. Finally, the statement updates 3 to 4 in pand the trigger updates all three rows in f from 3 to 4. Any changes to existing auditing options can also be audited to guard against malicious database activity. Therefore, a trigger body can prevent the execution of the triggering statement by raising an exception.

To disable the trigger reorder on the inventory table, enter the following statement: The trigger must correct the condition so the statement can be resumed.

Enabling and Disabling Triggers

If you omit schemathen Oracle Database assumes the trigger is in your own schema. You cannot define your own dispqradores. Although you can use both triggers and integrity constraints to define and enforce any type of integrity rule, Oracle strongly recommends that you use triggers to constrain data input only in the following situations: