Oracle PL/SQL Tutorial/Trigger/Before Event Trigger
Содержание
- 1 BEFORE EVENT triggers, are for preventing the event from actually happening
- 2 BEFORE INSERT OR UPDATE OF id
- 3 Change data in a before insert or update trigger
- 4 Check and change new value in a before-insert trigger
- 5 Check new value in before insert trigger
- 6 Check new value in before trigger
- 7 convert character values to upper case
- 8 Fire a trigger before an update of the table
- 9 Implementing Autonumbering Functionality
- 10 Insert before trigger
- 11 Use trigger to create autoincrement column
BEFORE EVENT triggers, are for preventing the event from actually happening
<source lang="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 emp_biu
2 before insert or update 3 on employee 4 referencing new as new old as old 5 for each row 6 begin 7 if :new.city = "VAN" and :new.salary < 1000 then 8 raise_application_error (-20999,"Wrong salary!"); 9 end if; 10 11 if :new.city = "VAN" and :new.salary >3000 then 12 raise_application_error (-20999,"Too much!"); 13 end if; 14 end; 15 /
Trigger created. SQL> SQL> SQL> SQL> update employee set salary = salary + salary, city="VAN"; update employee set salary = salary + salary, city="VAN"
*
ERROR at line 1: ORA-20999: Too much! ORA-06512: at "sqle.EMP_BIU", line 7 ORA-04088: error during execution of trigger "sqle.EMP_BIU"
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 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> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL> SQL></source>
BEFORE INSERT OR UPDATE OF id
<source lang="sql">
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 "sqle.CHECKID", line 10 ORA-04088: error during execution of trigger "sqle.CHECKID"
SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped.</source>
Change data in a before insert or update trigger
<source lang="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> CREATE OR REPLACE TRIGGER employee_insert_update
2 BEFORE INSERT OR UPDATE ON employee 3 FOR EACH ROW 4 DECLARE 5 dup_flag INTEGER; 6 BEGIN 7 --Force all employee names to uppercase. 8 :NEW.first_name := UPPER(:NEW.first_name); 9 END; 10 /
Trigger created. SQL> 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> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL></source>
Check and change new value in a before-insert trigger
<source lang="sql">
SQL> SQL> CREATE TABLE incremented_values
2 (value_inserted NUMBER, 3 value_incremented NUMBER);
Table created. SQL> SQL> CREATE OR REPLACE TRIGGER increment_by_one
2 BEFORE INSERT ON incremented_values 3 FOR EACH ROW 4 BEGIN 5 :new.value_incremented := :new.value_incremented + 1; 6 END; 7 /
Trigger created. SQL> SQL> CREATE OR REPLACE TRIGGER increment_by_two
2 BEFORE INSERT ON incremented_values 3 FOR EACH ROW 4 BEGIN 5 IF :new.value_incremented > 1 THEN 6 :new.value_incremented := :new.value_incremented + 2; 7 END IF; 8 END; 9 /
Trigger created. SQL> SQL> INSERT INTO incremented_values VALUES(1,1); 1 row created. SQL> SQL> SELECT * FROM incremented_values; VALUE_INSERTED VALUE_INCREMENTED
-----------------
1 2
SQL> SQL> SQL> DROP TABLE incremented_values; Table dropped. SQL></source>
Check new value in before insert trigger
<source lang="sql">
SQL> SQL> CREATE TABLE employee (
2 id number, 3 name varchar(100), 4 birth_date date, 5 gender varchar2(30) );
Table created. SQL> SQL> CREATE TRIGGER employee_bir
2 BEFORE INSERT ON employee 3 FOR EACH ROW 4 begin 5 if upper(:new.name) = "J" then 6 raise_application_error(20000, "Sorry, that genius is not allowed."); 7 end if; 8 end; 9 /
Trigger created. SQL> SQL> INSERT INTO employee (id,name,birth_date,gender )VALUES (100,"J",to_date("19230823", "YYYYMMDD"),"MALE" ); INSERT INTO employee (id,name,birth_date,gender )VALUES (100,"J",to_date("19230823", "YYYYMMDD"),"MALE" )
*
ERROR at line 1: ORA-21000: error number argument to raise_application_error of 20000 is out of range ORA-06512: at "sqle.EMPLOYEE_BIR", line 3 ORA-04088: error during execution of trigger "sqle.EMPLOYEE_BIR"
SQL> SQL> drop table employee; Table dropped.</source>
Check new value in before trigger
<source lang="sql">
SQL> SQL> CREATE TABLE game_player
2 (player_id NUMBER, 3 game_id NUMBER, 4 group_number NUMBER, 5 marked VARCHAR2(1) DEFAULT "N", 6 pcmac VARCHAR2(1) DEFAULT "N", 7 score NUMBER, 8 CONSTRAINT game_player_pk 9 PRIMARY KEY (player_id, game_id, group_number));
Table created. SQL> SQL> SQL> CREATE OR REPLACE TRIGGER set_score
2 BEFORE INSERT ON game_player 3 FOR EACH ROW 4 WHEN ( new.score IS NULL ) 5 BEGIN 6 IF :NEW.marked = "Y" THEN 7 :NEW.score := 10; 8 ELSIF :NEW.pcmac = "Y" THEN 9 :NEW.score := 5; 10 END IF; 11 END; 12 /
Trigger created. SQL> SQL> SQL> SQL> drop table game_player; Table dropped.</source>
convert character values to upper case
<source lang="sql">
SQL> SQL> create table employee
2 ( 3 empl_no integer primary key 4 ,lastname varchar2(20) not null 5 ,firstname varchar2(15) not null 6 ,midinit varchar2(1) 7 ,street varchar2(30) 8 ,city varchar2(20) 9 ,state varchar2(2) 10 ,zip varchar2(5) 11 ,zip_4 varchar2(4) 12 ,area_code varchar2(3) 13 ,phone varchar2(8) 14 ,company_name varchar2(50));
Table created. SQL> SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(1,"Jones","Joe","J","10 Ave","New York","NY","11111","1111","111", "111-1111","A Company");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(2,"Smith","Sue","J","20 Ave","New York","NY","22222","2222","222", "222-111","B Company");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(3,"Anderson","Peggy","J","500 St","New York","NY","33333","3333","333", "333-3333","C Company");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(4,"Andy","Jill", null,"930 St","New York","NY","44444","4444","212", "634-7733","D Company");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(5,"OK","Carl","L","19 Drive","New York","NY","55555","3234","212", "243-4243","E Company");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(6,"Peter","Jee","Q","38 Ave","New York","NY","66666","4598","212", "454-5443","F Inc");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(7,"Baker","Paul","V","738 St.","Queens","NY","77777","3842","718", "664-4333","G Inc");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(8,"Young","Steve","J","388 Ave","New York","NY","88888","3468","212", "456-4566","H Associates Inc");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(9,"Mona","Joe","T","9300 Ave","Kansas City","MO","99999","3658","415", "456-4563","J Inc");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(10,"Hackett","Karen","S","Kings Rd. Apt 833","Bellmore","NY","61202","3898","516", "767-5677","AA Inc");
1 row created. SQL> SQL> insert into employee(empl_no,lastname,firstname,midinit,street,city,state,zip,zip_4,area_code,phone,company_name)
2 values(11,"Bob","Jack","S","12 Giant Rd.","Newark","NJ","27377","3298","908", "123-7367","Z Associates");
1 row created. SQL> SQL> SQL> SQL> SQL> create trigger employee_name
2 before update or insert on employee
3 for each row
4 begin
5 /* convert character values to upper case */
6 :new.lastname := upper( :new.lastname );
7 :new.firstname := upper( :new.firstname );
8 dbms_output.put_line("trigger fired");
9 end;
10 /
Trigger created. SQL> SQL> SQL> insert into employee
2 (empl_no, firstname, lastname) 3 values 4 (3423, "dave", "anderson");
1 row created. SQL> SQL> select firstname, lastname
2 from employee 3 where empl_no = 3423;
FIRSTNAME LASTNAME
--------------------
DAVE ANDERSON SQL> SQL> SQL> drop table employee; Table dropped. SQL> SQL></source>
Fire a trigger before an update of the table
<source lang="sql">
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> SQL></source>
Implementing Autonumbering Functionality
<source lang="sql">
SQL> SQL> SQL> CREATE SEQUENCE idSeq; Sequence created. SQL> SQL> CREATE TABLE myTable (Name VARCHAR(50) PRIMARY KEY NOT NULL,
2 PhoneNo VARCHAR(15));
Table created. SQL> SQL> CREATE TABLE myTableAudit
2 (id INT PRIMARY KEY NOT NULL, 3 Operation VARCHAR(10), 4 RecordedOn DATE DEFAULT SysDate, 5 OldName VARCHAR(50), 6 NewName VARCHAR(50), 7 OldPhone VARCHAR(15), 8 NewPhone VARCHAR(15));
Table created. SQL> SQL> CREATE OR REPLACE TRIGGER idAutonumberTrigger
2 BEFORE INSERT ON myTableAudit 3 FOR EACH ROW 4 BEGIN 5 SELECT idSeq.NEXTVAL 6 INTO :NEW.id FROM DUAL; 7 END; 8 /
Trigger created. SQL> SQL> drop SEQUENCE idSeq; Sequence dropped. SQL> SQL> drop table myTable; Table dropped. SQL> SQL> drop table myTableAudit; Table dropped. SQL></source>
Insert before trigger
<source lang="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> CREATE OR REPLACE TRIGGER employee_insert_update
2 BEFORE INSERT OR UPDATE ON employee 3 FOR EACH ROW 4 DECLARE 5 dup_flag INTEGER; 6 BEGIN 7 --Force all employee names to uppercase. 8 :NEW.first_name := UPPER(:NEW.first_name); 9 END; 10 /
Trigger created. SQL> 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> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL></source>
Use trigger to create autoincrement column
<source lang="sql">
SQL> SQL> CREATE TABLE myTable (
2 myTableID INT PRIMARY KEY NOT NULL, 3 Name VARCHAR(50), 4 PhoneNo VARCHAR(15) DEFAULT "Unknown Phone");
Table created. SQL> SQL> CREATE SEQUENCE SEQ;
SQL> SQL> CREATE OR REPLACE TRIGGER AUTONUMBER
2 BEFORE INSERT ON myTable 3 FOR EACH ROW 4 BEGIN 5 SELECT SEQ.NEXTVAL 6 INTO :NEW.myTableID FROM DUAL; 7 END; 8 /
Trigger created. SQL> SQL> SQL> drop table myTable; Table dropped.</source>
