Oracle PL/SQL/Trigger/After Delete Trigger
Create an after delete 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> create table employee_audit (
2 id VARCHAR2(4 BYTE), 3 salary Number(8,2), 4 delete_date Date, 5 deleted_by VARCHAR2(15 BYTE) 6 ) 7 /
Table 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> SQL> SQL> CREATE OR REPLACE TRIGGER employee_after_delete
2 AFTER DELETE 3 ON employee 4 FOR EACH ROW 5 6 DECLARE 7 v_username varchar2(10); 8 9 BEGIN 10 11 -- Find username of person performing the DELETE on the table 12 SELECT user INTO v_username 13 FROM dual; 14 15 -- Insert record into audit table 16 INSERT INTO employee_audit (id, salary, delete_date, deleted_by) 17 VALUES ( :old.id, :old.salary, sysdate, v_username ); 18 19 END; 20 /
Trigger created. SQL> SQL> delete from employee; 8 rows deleted. SQL> SQL> select * from employee_audit; ID SALARY DELETE_DA DELETED_BY
---------- --------- ---------------
01 1234.56 09-SEP-06 sqle 02 6661.78 09-SEP-06 sqle 03 6544.78 09-SEP-06 sqle 04 2344.78 09-SEP-06 sqle 05 2334.78 09-SEP-06 sqle 06 4322.78 09-SEP-06 sqle 07 7897.78 09-SEP-06 sqle 08 1232.78 09-SEP-06 sqle 8 rows selected. SQL> SQL> drop table employee_audit; Table dropped. SQL> SQL> SQL> SQL> -- clean the table SQL> drop table Employee
2 /
Table dropped. SQL> SQL>
</source>
This is an example of a DML trigger.
<source lang="sql">
SQL> SQL> CREATE TABLE major_stats (
2 major VARCHAR2(30), 3 total_credits NUMBER, 4 total_students NUMBER);
Table created. SQL> SQL> INSERT INTO major_stats (major, total_credits, total_students) VALUES ("Computer Science", 22, 3); 1 row created. SQL> SQL> INSERT INTO major_stats (major, total_credits, total_students) VALUES ("History", 12, 3); 1 row created. SQL> SQL> INSERT INTO major_stats (major, total_credits, total_students) VALUES ("Economics", 15, 2); 1 row created. SQL> SQL> INSERT INTO major_stats (major, total_credits, total_students) VALUES ("Music", 11, 2); 1 row created. SQL> SQL> INSERT INTO major_stats (major, total_credits, total_students) VALUES ("Nutrition", 16, 2); 1 row created. SQL> SQL> SQL> CREATE TABLE students (
2 id NUMBER(5) PRIMARY KEY, 3 first_name VARCHAR2(20), 4 last_name VARCHAR2(20), 5 major VARCHAR2(30), 6 current_credits NUMBER(3) 7 );
Table created. SQL> SQL> SQL> CREATE OR REPLACE TRIGGER UpdateMajorStats
2 AFTER INSERT OR DELETE OR UPDATE ON students 3 DECLARE 4 CURSOR c_Statistics IS 5 SELECT major, COUNT(*) total_students, 6 SUM(current_credits) total_credits 7 FROM students 8 GROUP BY major; 9 BEGIN 10 DELETE FROM major_stats; 11 12 FOR v_StatsRecord in c_Statistics LOOP 13 INSERT INTO major_stats (major, total_credits, total_students) 14 VALUES (v_StatsRecord.major, v_StatsRecord.total_credits, 15 v_StatsRecord.total_students); 16 END LOOP; 17 END UpdateMajorStats; 18 /
Trigger created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10001, "Scott", "Lawson","Computer Science", 11);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major, current_credits)
2 VALUES (10002, "Mar", "Wells","History", 4);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10003, "Jone", "Bliss","Computer Science", 8);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10004, "Man", "Kyte","Economics", 8);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10005, "Pat", "Poll","History", 4);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10006, "Tim", "Viper","History", 4);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10007, "Barbara", "Blues","Economics", 7);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10008, "David", "Large","Music", 4);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10009, "Chris", "Elegant","Nutrition", 8);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10010, "Rose", "Bond","Music", 7);
1 row created. SQL> SQL> INSERT INTO STUDENTS (id, first_name, last_name, major,current_credits)
2 VALUES (10011, "Rita", "Johnson","Nutrition", 8);
1 row created. SQL> SQL> INSERT INTO students (id, first_name, last_name, major,current_credits)
2 VALUES (10012, "Sharon", "Clear","Computer Science", 3);
1 row created. SQL> SQL> select * from major_stats; MAJOR TOTAL_CREDITS TOTAL_STUDENTS
------------- --------------
Computer Science 22 3 Economics 15 2 Nutrition 16 2 History 12 3 Music 11 2 SQL> SQL> drop table students; Table dropped. SQL> drop table major_stats; Table dropped.
</source>
