Oracle PL/SQL/Trigger/Before Update Trigger
Check new value before insert and update
<source lang="sql">
SQL> SQL> CREATE TABLE MyTable (
2 num_col NUMBER, 3 char_col VARCHAR2(60) 4 );
Table created. SQL> SQL> SQL> CREATE OR REPLACE TRIGGER OnlyPositive
2 BEFORE INSERT OR UPDATE OF num_col 3 ON MyTable 4 FOR EACH ROW 5 BEGIN 6 IF :new.num_col < 0 THEN 7 RAISE_APPLICATION_ERROR(-20100, "Please insert a positive value"); 8 END IF; 9 END OnlyPositive; 10 /
Trigger created. SQL> SQL> INSERT INTO MyTable (num_col, char_col)
2 VALUES (1, "This is row 1");
1 row created. SQL> SQL> INSERT INTO MyTable (num_col, char_col)
2 VALUES (-1, "This is row -1");
INSERT INTO MyTable (num_col, char_col)
*
ERROR at line 1: ORA-20100: Please insert a positive value ORA-06512: at "sqle.ONLYPOSITIVE", line 3 ORA-04088: error during execution of trigger "sqle.ONLYPOSITIVE"
SQL> SQL> drop table MyTable; Table dropped. SQL> SQL>
</source>
Create a "BEFORE UPDATE" Trigger
<source lang="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> -- BEFORE UPDATE Trigger SQL> CREATE OR REPLACE TRIGGER employee_before_update
2 BEFORE UPDATE
3 ON employee
4 FOR EACH ROW
5
6 DECLARE
7 v_username varchar2(10);
8
9 BEGIN
10 -- Find username of person performing UPDATE on the table
11 SELECT user INTO v_username
12 FROM dual;
13
14 dbms_output.put_line("By: "||v_username);
15 dbms_output.put_line("Date: "||sysdate);
16 dbms_output.put_line(":new.id: "||:new.id);
17 dbms_output.put_line(":new.first_name: "||:new.first_name);
18 dbms_output.put_line(":new.last_name: "||:new.last_name);
19 dbms_output.put_line(":old.id: "||:old.id);
20 dbms_output.put_line(":old.first_name: "||:old.first_name);
21 dbms_output.put_line(":old.last_name: "||:old.last_name);
22
23 END;
24 /
Trigger created. SQL> SQL> update employee set first_name="newName"; By: sqle Date: 09-SEP-06
- new.id: 01
- new.first_name: newName
- new.last_name: Martin
- old.id: 01
- old.first_name: Jason
- old.last_name: Martin
By: sqle Date: 09-SEP-06
- new.id: 02
- new.first_name: newName
- new.last_name: Mathews
- old.id: 02
- old.first_name: Alison
- old.last_name: Mathews
By: sqle Date: 09-SEP-06
- new.id: 03
- new.first_name: newName
- new.last_name: Smith
- old.id: 03
- old.first_name: James
- old.last_name: Smith
By: sqle Date: 09-SEP-06
- new.id: 04
- new.first_name: newName
- new.last_name: Rice
- old.id: 04
- old.first_name: Celia
- old.last_name: Rice
By: sqle Date: 09-SEP-06
- new.id: 05
- new.first_name: newName
- new.last_name: Black
- old.id: 05
- old.first_name: Robert
- old.last_name: Black
By: sqle Date: 09-SEP-06
- new.id: 06
- new.first_name: newName
- new.last_name: Green
- old.id: 06
- old.first_name: Linda
- old.last_name: Green
By: sqle Date: 09-SEP-06
- new.id: 07
- new.first_name: newName
- new.last_name: Larry
- old.id: 07
- old.first_name: David
- old.last_name: Larry
By: sqle Date: 09-SEP-06
- new.id: 08
- new.first_name: newName
- new.last_name: Cat
- old.id: 08
- old.first_name: James
- old.last_name: Cat
8 rows updated. SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL>
</source>
Create a BEFORE UPDATE trigger on the emp table
<source lang="sql">
SQL> CREATE TABLE emp (
2 id NUMBER PRIMARY KEY, 3 fname VARCHAR2(50), 4 lname VARCHAR2(50) 5 );
Table created. SQL> SQL> INSERT INTO emp (id, fname, lname)VALUES (1, "A", "B"); 1 row created. SQL> INSERT INTO emp (id, fname, lname)VALUES (2, "C", "D"); 1 row created. SQL> INSERT INTO emp (id, fname, lname)VALUES (3, "E", "F"); 1 row created. SQL> INSERT INTO emp (id, fname, lname)VALUES (4, "G", "H"); 1 row created. SQL> INSERT INTO emp (id, fname, lname)VALUES (5, "G", "Z"); 1 row created. SQL> SQL> SQL> SET SERVEROUTPUT ON SQL> SQL> SQL> CREATE OR REPLACE TRIGGER emp_trig
2 BEFORE UPDATE OF fname
3 ON emp
4 FOR EACH ROW
5 BEGIN
6 DBMS_OUTPUT.PUT_LINE("First Name "||:OLD.fname||" has change to "||:NEW.fname);
7 END;
8 /
Trigger created. SQL> SQL> SQL> SELECT trigger_name, status FROM user_triggers; TRIGGER_NAME STATUS
--------
EMP_TRIG ENABLED INVENTORY_TRG DISABLED DEMO_BIFER DISABLED DEPT_SAL_TRG DISABLED SYSTEMALTERUSER DISABLED USAGE_START DISABLED USAGE_STOP DISABLED USER_LOGON_MODULE_CHECK DISABLED 8 rows selected. SQL> SQL> drop table emp; Table dropped. SQL>
</source>
