Firing a Trigger : Trigger « Trigger « Oracle PL/SQL Tutorial






SQL>
SQL>
SQL>
SQL> create table myaudit(
  2     id VARCHAR2(4 BYTE)         NOT NULL,
  3     old_value VARCHAR2(40 BYTE),
  4     new_value VARCHAR2(40 BYTE)
  5  );

Table created.

SQL>
SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /

Table created.

SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ('01','Jason',    'Martin',  to_date('19960725','YYYYMMDD'), to_date('20060725','YYYYMMDD'), 1234.56, 'Toronto',  'Programmer')
  3  /

1 row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('02','Alison',   'Mathews', to_date('19760321','YYYYMMDD'), to_date('19860221','YYYYMMDD'), 6661.78, 'Vancouver','Tester')
  3  /

1 row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('03','James',    'Smith',   to_date('19781212','YYYYMMDD'), to_date('19900315','YYYYMMDD'), 6544.78, 'Vancouver','Tester')
  3  /

1 row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('04','Celia',    'Rice',    to_date('19821024','YYYYMMDD'), to_date('19990421','YYYYMMDD'), 2344.78, 'Vancouver','Manager')
  3  /

1 row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values('05','Robert',   'Black',   to_date('19840115','YYYYMMDD'), to_date('19980808','YYYYMMDD'), 2334.78, 'Vancouver','Tester')
  3  /

1 row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('06','Linda',    'Green',   to_date('19870730','YYYYMMDD'), to_date('19960104','YYYYMMDD'), 4322.78,'New York',  'Tester')
  3  /

1 row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('07','David',    'Larry',   to_date('19901231','YYYYMMDD'), to_date('19980212','YYYYMMDD'), 7897.78,'New York',  'Manager')
  3  /

1 row created.

SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('08','James',    'Cat',     to_date('19960917','YYYYMMDD'), to_date('20020415','YYYYMMDD'), 1232.78,'Vancouver', 'Tester')
  3  /

1 row created.

SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
  2  /

ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester

8 rows selected.

SQL>
SQL>
SQL>
SQL> CREATE OR REPLACE TRIGGER before_employee_salary_update
  2  BEFORE UPDATE OF salary
  3  ON employee
  4  FOR EACH ROW WHEN (new.salary < old.salary * 0.75)
  5  BEGIN
  6    dbms_output.put_line('id = ' || :old.id);
  7    dbms_output.put_line('Old salary = ' || :old.salary);
  8    dbms_output.put_line('New salary = ' || :new.salary);
  9    dbms_output.put_line('The salary reduction is more than 25%');
 10
 11  INSERT INTO Myaudit (
 12    id, old_value, new_value
 13  ) VALUES (
 14    :old.id, :old.salary, :new.salary
 15  );
 16  END before_employee_salary_update;
 17  /

Trigger created.

SQL>
SQL> update employee set salary = 0;

8 rows updated.

SQL>
SQL>
SQL> select * from employee;

ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06          0 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86          0 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90          0 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99          0 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98          0 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96          0 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98          0 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02          0 Vancouver  Tester

8 rows selected.

SQL>
SQL> select * from myaudit;

ID   OLD_VALUE                                NEW_VALUE
---- ---------------------------------------- ----------------------------------------
01   1234.56                                  0
02   6661.78                                  0
03   6544.78                                  0
04   2344.78                                  0
05   2334.78                                  0
06   4322.78                                  0
07   7897.78                                  0
08   1232.78                                  0

8 rows selected.

SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /

Table dropped.

SQL>
SQL> drop table myaudit;

Table dropped.

SQL>
SQL>








28.2.Trigger
28.2.1.Triggers
28.2.2.System triggers
28.2.3.Creating a Trigger
28.2.4.Trigger Blocks
28.2.5.Trigger that output old value
28.2.6.DML Trigger Example
28.2.7.Firing a Trigger
28.2.8.The use of a trigger
28.2.9.INSERTING, DELETING and UPDATING Predicates
28.2.10.Reference current user name in trigger
28.2.11.Call raise_application_error to report an error in a trigger
28.2.12.Use cursor in trigger
28.2.13.Check the status of the trigger
28.2.14.Show errors for a trigger