examples on trigger

8/7/2019 examples on trigger

1/18

Example: create a trigger on employee table called EMP to add rows on the table calledAUDIT_EMP_TABLE to trace any update operation on the table EMP. The triggershould store the old and new values of the different columns.


2/18

Use the USER_TRIGGERS data dictionary view to display information about the RESTRICT_SAL trigger.

SQL> SELECT trigger_name,trigger_type,

2 triggering_event, table_name,

referencing_names, when_clause, status,trigger_body

4 FROM user_triggers

5 WHEREtrigger_name = 'RESTRICT_SAL';


3/18

You can create a BEFORE statement trigger in order to prevent the triggering operation from succeeding if a certain condition isviolated.Create a trigger to restrict inserts into the EMP table to certain business hours, Monday through Friday.If a user attempts to insert a row into the EMP table on Saturday, for example, the user sees the message, the trigger fails, and thetriggering statement is rolled back. RAISE_APPLICATION_ERROR is a server-side built-in procedure that returns an error to theuser and causes the PL/SQL block to fail.

SQL> CREATE OR REPLACE TRIGGER secure_emp2 BEFORE INSERT ON emp3 BEGIN

4 IF (TO_CHAR (sysdate,'DY') IN ('SAT','SUN')) OR5 (TO_CHAR(sysdate,'HH24') NOT BETWEEN6 '08' AND '18')7 THEN RAISE_APPLICATION_ERROR (-20500,

8 'You may only insert into EMP during business hours.');9 END IF;10 END;


4/18

Creating Statement Triggers

Using Procedure Builder

Creating Statement Triggers

Using Procedure Builder


5/18

Using Conditional PredicatesCREATE OR REPLACE TRIGGER secure_empBEFORE INSERT OR UPDATE OR DELETE ON empBEGINIF (TO_CHAR (sysdate,'DY') IN ('SAT','SUN')) OR

(TO_CHAR (sysdate, 'HH24') NOT BETWEEN '08' AND '18')THEN

IF DELETINGTHEN RAISE_APPLICATION_ERROR (-20502,'You may only delete from EMP during normal hours.');ELSIF INSERTINGTHEN RAISE_APPLICATION_ERROR (-20500,

'You may only insert into EMP during normal hours.');ELSIF UPDATING ('SAL')THEN RAISE_APPLICATION_ERROR (-20503,

'You may only update SAL during normal hours.');ELSERAISE_APPLICATION_ERROR (-20504,'You may only update EMP during normal hours.');

END IF;END IF;

END;


6/18

ExamplesA triger to return back to the first record

if the pointer reach the last record. The trigger on the level of : BLOCK

type : KEY-DOWN

IF :SYSTEM.LAST-RECORD =TRUETHENFIRST-RECORD;

ELSENEXT_RECORD;END IF;


7/18

Trigger To show the time on a form

trigger on the level of form

type : when _new form_instance

DECLARET TIMER ;BEGINT:=CREATE _TIMER ('TI',1000,REPEAT);END;

there shoulb be another TRIGGER to finish the first :level of TRIGGER : form

type : WHEN_TIMER_EXPIRED

:CLOCK :=TO_CHAR(SYSDATE,'HH:MI:SS');

where the name : CLOCK is DISPLAY ITEM


8/18

the trigger will maximize the window on run time level of trigger is form

type =when_new_form instance

beginset_window_property(forms_mdi_window,title,' ');set_window_property(forms_mdi_window,window_state,maximize);

set_window_property('window1',window_state,maximize);end;


9/18

A Trigger To Run A Report From A

Formtype : when_button_pressed

level : on button

declarepl_id number;beginrun_product(reports,'emp.rep',synchronous,runtime,filesystem,

pl_id,null);end;

whereemp =report name


10/18

: foreign key

: post-query

: block

customers (city_number) foreign key

(master table) cities_table (city_no, city_name)

:

:display item c_name database item = No

post-query

DECLARECURSOR c1 IS SELECT city_name FROM cities_table WHERE city_no = :customers.city_number

BEGINOPEN c1;

FETCH c1 INTO :customers.c_name;IF c1%NOTFOUND THEN

:customers.c_name := 'not available' ;END IF;

CLOSE c1;END;

1)

2) list of valuewhen-validate-itemtrigger

3) when_validate_item : :customers.city_number

4) post-query & when-validate-item :post-change .


11/18

=inv_d =items

=

= pre_insert= data block

declarea number ;beginselect items.qty into a from item where items.item_no=:inv_d.item_no;

if :inv_d.qty>a thenmessage(' ');raise form_trigger_failure;elseupdate items set qty=qty-:inv_d.qty where item_no=:inv_d.item_no ;end if;end


12/18

PASING PARAMETER BETWEEN FORMS

DEPT 20 EMP

DEPT F3 PARAMETERS NO PARAMETER DATA TYPENUMBER

DEPTNO . DEPT EMPTABULAR EMP ..

WHEN_BUTTON_PREESED DECLARE

A PARAMLIST;BEGIN

A:=CREATE_PARAMETER_LIST('THA');ADD_PARAMETER(A,'NO',TEXT_ITEM,PARAMETER,:DEPTNO);

RUN_PRODUCT(FORMS,'EMP',ASY

NCHRONOUS,RUNTIME,FILESY

STEM,A,'');EXIT_FORM;END;

..

TRIGEER WHEN_NEW_FORM_INSTANCE :

DECLARE

B BLOCK;BEGINB:=FIND_BLOCK('EMP');

IF(:PARAMETER.NO IS NOT NULL)THENSET_BLOCK_PROPERTY(B,DEFAULT_WHERE,'DEPTNO='||:PARAMETER.NO);

GO_BLOCK('EMP');EXECUTE_QUERY;

END IF;END;


13/18

exe

host('"c:\winnt\notepad.exe")


14/18

username/password fmx

. (ON-LOGON)

:

LOGON('SCOTT','TIGER@SERVICE_NAEM');


15/18

You can create this trigger to monitor how often you log on and off, or you maywant to write a report on how long you are logged on for. When you specify ONSCHEMA,the trigger fires for the specific user. If you specify ON DATABASE, thetrigger fires for all users


16/18

Sample LOG_TRIG_TABLE:SQL> describe log_trig_tableName Null? Type------------------------------- -------- ----USER_ID VARCHAR2(30)LOG_DATE DATEACTION VARCHAR2(30)

SQL> select * from log_trig_table;

USER_ID LOG_DATE ACTION-------------------------- --------- ---------------------A_USER 23-MAR-99 Logging offA_USER 23-MAR-99 Logging on


17/18

The following example creates a logon statistics table and a LOGON and LOGOFF databasetrigger to capture the time when a user connects/disconnects to/from the database.

CREATE TABLE session_logon_statistics

(user_logged VARCHAR2(30),start_time DATE,end_time DATE);

CREATE OR REPLACE TRIGGER logon_log_triggerAFTER LOGONON DATABASE

BEGININSERT INTO session_logon_statistics(user_logged, start_time)VALUES(USER, SYSDATE);END;/

CREATE OR REPLACE TRIGGER logoff_log_triggerBEFORE LOGOFFON DATABASEBEGINUPDATE session_logon_statisticsSET end_time = SYSDATEWHERE user_logged = USERAND end_time IS NULL;END


18/18

The following script retrieves the information from the session_logon_statistics table.

SELECT user_logged,

TO_CHAR(start_time, 'MM/DD/YYYY HH24:MI:SS')"START TIME",

TO_CHAR(end_time, 'MM/DD/YYYY HH24:MI:SS')"END TIME"

FROM session_logon_statistics

order by user_logged, start_time;

examples on trigger

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