Trigger Which Modifies a Mutating Table : Introduction « Trigger « Oracle PL/SQL Tutorial






SQL>
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>
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

4 rows selected.

SQL>
SQL>
SQL>
SQL> CREATE OR REPLACE TRIGGER LimitSalary
  2    BEFORE INSERT OR UPDATE OF salary ON employee
  3    FOR EACH ROW
  4  DECLARE
  5    v_MaxSalary CONSTANT NUMBER := 2000;
  6    v_CurrentSalary NUMBER;
  7  BEGIN
  8    SELECT salary
  9      INTO v_CurrentSalary
 10      FROM employee
 11      WHERE id = :new.id;
 12
 13    IF v_CurrentSalary > v_MaxSalary THEN
 14      RAISE_APPLICATION_ERROR(-20000, 'Too high in salary ' || :new.id);
 15    END IF;
 16  END LimitSalary;
 17  /

Trigger created.

SQL>
SQL>
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  /
insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,               Salary,  City,       Description)
            *
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "JAVA2S.LIMITSALARY", line 5
ORA-04088: error during execution of trigger 'JAVA2S.LIMITSALARY'


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  /
insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,               Salary, City,        Description)
            *
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "JAVA2S.LIMITSALARY", line 5
ORA-04088: error during execution of trigger 'JAVA2S.LIMITSALARY'


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  /
insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,               Salary, City,        Description)
            *
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "JAVA2S.LIMITSALARY", line 5
ORA-04088: error during execution of trigger 'JAVA2S.LIMITSALARY'


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  /
insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,               Salary, City,        Description)
            *
ERROR at line 1:
ORA-01403: no data found
ORA-06512: at "JAVA2S.LIMITSALARY", line 5
ORA-04088: error during execution of trigger 'JAVA2S.LIMITSALARY'


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    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

4 rows selected.

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

Table dropped.

SQL>
SQL>








28.1.Introduction
28.1.1.A trigger is an event within the DBMS that can cause some code to execute automatically.
28.1.2.Placing triggers on tables
28.1.3.Trigger Which Modifies a Mutating Table
28.1.4.Solution for the Mutating Tables Problem
28.1.5.Raise Exception from trigger
28.1.6.Trigger for auditing
28.1.7.Trigger with a REFERENCING clause
28.1.8.Trigger with REFERENCING and WHEN clauses
28.1.9.Trigger with multiple triggering events