Write a trigger before insert the record of the student in the Student table.

Write a trigger before insert the record of the student in the Student

table. If the Roll_No is less than or equal to zero then the trigger

gets fired and displays the message “Invalid Roll Number”.

Write a trigger before insert the record of the student in the Student

table. If the Roll_No is less than or equal to zero then the trigger

gets fired and displays the message “Invalid Roll Number”.

--->>

 create or replace function less() returns trigger as

'

 declare

begin

if new.rollno <= 0 then 

 raise exception ''rollno is not valide'';

end if;

 return new;

 end;

'language 'plpgsql';

Create  trigger 

create  trigger vasi

before insert on student

for each row execute procedure less();

output of Trigger

Acode3=#  insert into student values (-1,'abc','fy'  );

o\p

Acode3=#  insert into student values (-1,'abc','fy'  );

ERROR:  rollno is not valide