BEFORE INSERT OR UPDATE OF id : Before Event Trigger « Trigger « Oracle PL/SQL Tutorial






SQL>
SQL>
SQL>
SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL primary key,
  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 CheckID
  2    BEFORE INSERT OR UPDATE OF id
  3    ON employee
  4    FOR EACH ROW
  5  DECLARE
  6    v_ID  NUMBER(5);
  7  BEGIN
  8    SELECT id
  9      into v_ID
 10      FROM employee
 11      where id = :new.id;
 12  EXCEPTION
 13    WHEN NO_DATA_FOUND THEN
 14      RAISE_APPLICATION_ERROR(-20000, :new.id || ' is not a ' ||' valid ID');
 15  END CheckID;
 16  /

Trigger created.

SQL>
SQL>
SQL> update employee set salary = 1000;

8 rows updated.

SQL>
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values('99','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-20000: 99 is not a  valid ID
ORA-06512: at "JAVA2S.CHECKID", line 10
ORA-04088: error during execution of trigger 'JAVA2S.CHECKID'


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

Table dropped.








28.6.Before Event Trigger
28.6.1.BEFORE EVENT triggers, are for preventing the event from actually happening
28.6.2.Insert before trigger
28.6.3.Check and change new value in a before-insert trigger
28.6.4.Fire a trigger before an update of the table
28.6.5.Change data in a before insert or update trigger
28.6.6.BEFORE INSERT OR UPDATE OF id
28.6.7.Check new value in before insert trigger
28.6.8.Check new value in before trigger
28.6.9.convert character values to upper case
28.6.10.Use trigger to create autoincrement column
28.6.11.Implementing Autonumbering Functionality