WITH product_po AS (
    SELECT C.product_id, A.ref_doc_no, B.ref_item_amount
    FROM pu_po_internal_doc_no A
    INNER JOIN sl_invoice_item B ON B.invoice_id = A.ref_id
    INNER JOIN sl_do_item C ON C.do_item_id = B.ref_item_id
    WHERE A.ref_doc_type_id = 321
        AND A.po_internal_id IN (
            SELECT po_internal_id
            FROM pu_po_internal_doc_no A
            INNER JOIN pu_po B ON B.po_id = A.ref_id
            WHERE A.ref_doc_type_id = 101 AND A.ref_doc_no = 'GOP/00841/201612' AND B.ou_id = 12
        )
)
SELECT A.doc_no AS so_no, A.doc_date AS so_date,
f_get_product_code(B.product_id) AS product_code, f_get_product_name(B.product_id) AS product_code,
B.nett_item_amount AS so_item_amount, C.ref_doc_no AS sales_invoice_no, C.ref_item_amount AS sales_invoice_item_amount, A.curr_code
FROM sl_so A
INNER JOIN sl_so_item B ON B.so_id = A.so_id
LEFT JOIN product_po C ON C.product_id = B.product_id
WHERE A.doc_no = 'GSON/02114/201612' AND A.ou_id = 13