mysql trigger after update is not working - mysql

Question

This trigger is supposed to update the free rooms available for a hospital.When a patient leaves the trigger adds one more free room.But it just doesn't work and I really cannot understand why.I use these tables for this trigger:
create table Incidents
(primary key(incident_code),
foreign key(patient_code) references Patients(patient_code)on delete cascade on update cascade,
foreign key(section_code) references Sections(section_code)on delete cascade on update cascade,
foreign key(doctor_code) references Doctors(doctor_code)on delete cascade on update cascade,
incident_code int unsigned,
patient_code int unsigned,
section_code int unsigned,
doctor_code int unsigned,
import_day date not null,
export_day date,
incident_value real not null
check(datediff(export_day,import_day)>-1));
(primary key(section_code),
section_code int unsigned,
section_name varchar(30) not null,
total_rooms int not null,
free_rooms int not null
check(total_rooms>=free_rooms));
this is the triggers code:
delimiter #
create trigger FreeRooms1
after update on incidents
for each row
begin
if (old.export_day=null and new.export_day != null)
then
update sections
set free_rooms = free_rooms + 1
where sections.section_code = incidents.section_code;
end if;
end;
#
And this is how I try to activate it:
update incidents
set export_day = '2013/12/24'
where incident_code = 2;
select section_code,section_name,free_rooms
from sections;
I tried many variations for the trigger but any change I make doesn't make work.Any help?
Sorry if my question seems bad I am fairly new to mySQL and I can't find an answer anywhere.

Answer 1

I think you should use:
delimiter #
create trigger FreeRooms1
after update on incidents
for each row
begin
if (old.export_day IS NULL and new.export_day IS NOT NULL)
then
update sections
set free_rooms = free_rooms + 1
where sections.section_code = NEW.section_code;
end if;
end;
#
and reference the new row.