Try:

SELECT invoice.client_name, item_invoice.item_hscode;
 FROM ;
     invoice ;
    INNER JOIN item_invoice ;
   ON  invoice.inv_no = item_invoice.inv_no;
 WHERE  item_invoice.item_hscode = 8899009900

>i have two table
>
>
>(table invoice) = inv_no,trans_no,client_code,client_name
>
>and
>
>(table item_invoice) = inv_no,trans_no,item_hscode
>
>
>
>so i want to retrieve all the client name that have the item_hscode 8899009900
>
>
>so how can i do that
>
>thanks