Untitled

17/02/2024
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Trigger:

A Trigger is user defined cammand that is invoked automatically in responce to event such as insert ,delete and update.

or

Trigger are store program/ procedure ,which are automatically execute or fixed when somee event occure.
Each trigger is associated with a table which is activeted any dml cammandsuch as insert update and delete.

syntax:
create Trigger trigger_name trigger_time
trigger event on table_name for each row
Begin
.........
end ;

trigger time: before ,after

trigger event: insert ,update,delete
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use triggerexa;

-- create table employee(emp_id int ,name varchar(222),age int,salary int);

delimiter //
create trigger age_validate
before insert on employee for each row
begin
if new.age <0 then set new.age=0 ;
end if ; 
end//

-- delimiter ;
insert into employee values(4,"tanush",12,200000),(5,"neha",2,400000),(6,"sita",67,100000) ;

 select * from employee;

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Drop the triiger:

synatx:-
drop trigger trigger_name;

exa:-drop trigger age_validate

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Q1.  Write a pl-sql code which insert the data automatically into "backup" table whenever data is deleted from main table;
create table empback(emp_id int ,name varchar(222),age int,salary int);


delimiter $$
create trigger databack
before delete  on employee
for each row
begin
insert into empback values(old.emp_id,old.name,old.age,old.salary);
end $$