Trigger updating more than reqiured rows

Question

Hi guys, I have the trigger below on my db, the trigger is suppose to update a column "Total_qty" in tbl_supply_s table with a value "qty_sold" from vw_receipt_pos. but depending on the number of record that was entered from the application, the triger doubles the update. take for instance, if someone enters two rows with qty_sold = 2 for the two rows, the triger updates total_qty to minus 8 instead of minus 4.
Pls guys help me look at the triger n tell me the problem. thanks
CREATE OR REPLACE TRIGGER "TRG_UPDATE_TOTAL_QTY"
AFTER insert on "TBL_SALES_DETAILS"
begin
declare
v_sales_id number;
v_supply_id number;
v_qty number;
     CURSOR cur_update_total IS SELECT distinct supply_id, qty_sold FROM VW_RECEIPT_POS where sales_id = (select max(sales_id) from tbl_sales_s);
begin
select max(sales_id) into v_sales_id from tbl_sales_s;
OPEN cur_update_total;
LOOP
FETCH cur_update_total INTO v_supply_id, v_qty;
EXIT WHEN cur_update_total%NOTFOUND;
update tbl_supply_s
set total_qty = total_qty - v_qty
where supply_id = v_supply_id;
END LOOP;
CLOSE cur_update_total;
end;
end;

Answer 1

Hi!
This is the wrong forum to ask SQL or PL/SQL questions!
Please ask your question here:
PL/SQL
Best regards,
Matt