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In the list of choices, click New Trigger. In the list of schema object types, right-click Triggers. In the Connections frame, expand hr_conn. NEW_EVALUATION_TRIGGER is a row-level trigger and a BEFORE trigger. The trigger fires once for each row affected by the triggering INSERT statement.
ORACLE SQL DEVELOPER TUTORIAL HOW TO
This tutorial shows how to use the SQL Developer Create Trigger tool to create a trigger named NEW_EVALUATION_TRIGGER, which fires before a row is inserted into the EVALUATIONS table, and generates the unique number for the primary key of that row, using EVALUATIONS_SEQUENCE. However, these primary keys are not inserted into the table automatically. The sequence EVALUATIONS_SEQUENCE (created in "Tutorial: Creating a Sequence") generates primary keys for the EVALUATIONS table (created in "Creating Tables"). Tutorial: Creating a Trigger that Generates a Primary Key for a Row Before It Is Inserted INSERT INTO EVALUATIONS_LOG (log_date, action)
ORACLE SQL DEVELOPER TUTORIAL CODE
To create EVALUATIONS_LOG and EVAL_CHANGE_TRIGGER:ĬREATE TABLE EVALUATIONS_LOG ( log_date DATEĬREATE OR REPLACE TRIGGER EVAL_CHANGE_TRIGGERĭBMS_OUTPUT.PUT_LINE('This code is not reachable.') The trigger adds the row after the triggering statement executes, and uses the conditional predicates INSERTING, UPDATING, and DELETING to determine which of the three possible DML statements fired the trigger.ĮVAL_CHANGE_TRIGGER is a statement-level trigger and an AFTER trigger.
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This tutorial shows how to use the CREATE TRIGGER statement to create a trigger, EVAL_CHANGE_TRIGGER, which adds a row to the table EVALUATIONS_LOG whenever an INSERT, UPDATE, or DELETE statement changes the EVALUATIONS table. Tutorial: Creating a Trigger that Logs Table Changes For other uses of triggers, see Oracle Database PL/SQL Language Reference. 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. A trigger on the table can ensure the proper format of all data added to it. For example, suppose that data added to the EMPLOYEES table must have a certain format, and that many client applications can add data to this table. One use of triggers is to enforce business rules that apply to all client applications. A trigger defined on a database fires for each event associated with all users. A trigger defined on a schema fires for each event associated with the owner of the schema (the current user). For more information, see "Creating an INSTEAD OF Trigger".Ī system trigger is defined on a schema or the database.
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Instead of executing the DML statement, Oracle Database executes the INSTEAD OF trigger. For information about compound triggers, see Oracle Database PL/SQL Language Reference.Īn INSTEAD OF trigger is defined on a view, and its triggering event is a DML statement. You might be unaware that a trigger is executing unless it causes an error that is not handled properly.Ī simple trigger can fire at exactly one of these timing points:īefore the triggering event executes ( statement-level BEFORE trigger)Īfter the triggering event executes (statement-level AFTER trigger)īefore each row that the event affects ( row-level BEFORE trigger)Īfter each row that the event affects (row-level AFTER trigger)Ī compound trigger can fire at multiple timing points. A trigger is invoked only by its triggering event, which can be caused by any user or application. Unlike a subprogram, a trigger cannot be invoked directly. You can disable an enabled trigger, and enable a disabled trigger. If the trigger is in the disabled state, the triggering_event does not cause the database to execute the triggered_action, even if the trigger_restriction is TRUE or omitted.īy default, a trigger is created in the enabled state. The triggering_event is associated with either a table, a view, a schema, or the database, and it is one of these:ĭML statement (described in "About Data Manipulation Language (DML) Statements")ĭDL statement (described in "About Data Definition Language (DDL) Statements")ĭatabase operation ( SERVERERROR, LOGON, LOGOFF, STARTUP, or SHUTDOWN) If the trigger is in the enabled state, the triggering_event causes the database to execute the triggered_action if the trigger_restriction is either TRUE or omitted. 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. The trigger_name must be unique for triggers in the schema. A trigger is a PL/SQL unit that is stored in the database and (if it is in the enabled state) automatically executes ("fires") in response to a specified event.