automated alert emails using sql developer - oracle

Question

A supermarket has many products. When one of these products reaches a quantity of zero an automated email needs to be sent to the manager, showing that this product is out of stock.
I have done the email part( sending email through SQL Developer ). Now I need to set up a loop to keep tracking the products' quantity. How is this loop called? .
APC? i tried this out. but its not working for me
create or replace
procedure check_stock_qty
begin
for r in ( select product_name,product_id from super_market
where pro_qty = 0 )
loop
UTL_MAIL.send(sender => 'blabla#me.com',
recipients => 'blabla#me.com',
subject => 'Test Mail',
message => ( r.product_name ),
mime_type => 'text; charset=us-ascii');
end loop;
end;
------------------------
BEGIN
dbms_scheduler.create_job (job_name => 'stock check',
job_type => 'PLSQL_BLOCK',
job_action => 'BEGIN check_stock_qty; END;',
start_date => SYSTIMESTAMP,
repeat_interval => 'freq=minutely; interval=5; bysecond=0;',
end_date => NULL,
enabled => TRUE,
END;
the procedure compiled, but win run it. it gives an error " the selected program is in an invalid state for running. recompile the program and try again "

Answer 1

The best way to do this would be to use a database job to periodically check the PRODUCTS table.
First of all you need a stored procedure. Something like this:
create or replace procedure check_stock_qty
begin
for r in ( select product_name from products
where qty = 0 )
loop
your_email_proc_here ( r.product_name );
end loop;
end;
You would then set this to run at regular intervals. As you're using Oracle 11g you should use the DBMS_SCHEDULER API to do this. This calll will run the above stock checker every five minutes:
BEGIN
dbms_scheduler.create_job (
job_name => 'stock check',
job_type => 'PLSQL_BLOCK',
job_action => 'BEGIN check_stock_qty; END;',
start_date => SYSTIMESTAMP,
repeat_interval => 'freq=minutely; interval=5; bysecond=0;',
end_date => NULL,
enabled => TRUE,
END;
/
DBMS_SCHEDULER is pretty sophisticated i.e. complicated but it is well documented. Find out more.