Getting Sum Using PL/SQL In Optimized Way - oracle

Question

I have the below PL/SQL block which would be converted to a function, this would be used very heavily, is there a better and efficient way to re-write in the most optimized way?
Appreciate any suggestions or insights.
DECLARE
ln_grand_total NUMBER;
ln_total NUMBER;
ln_final_total NUMBER;
CURSOR E1
IS
SELECT SUM (qty * price * rate)
INTO ln_total
FROM maximo.po_lines pl
JOIN maximo.po_headers ph ON pl.HEADER_ID = ph.HEADER_ID
WHERE ph.HEADER_ID = 0123;
BEGIN
OPEN E1;
FETCH E1 INTO ln_grand_total;
ln_final_total := ROUND (ln_grand_total, 2);
DBMS_OUTPUT.put_line (ROUND (ln_grand_total, 2));
CLOSE E1;
DBMS_OUTPUT.put_line ('ln_final_total --> ' || ln_final_total);
END;
/

Answer 1

You don't need a cursor for this:
DECLARE
ln_total NUMBER;
BEGIN
SELECT ROUND( SUM (qty * price * rate), 2 )
INTO ln_total
FROM maximo.po_lines pl
JOIN maximo.po_headers ph
ON pl.HEADER_ID = ph.HEADER_ID
WHERE ph.HEADER_ID = 0123;
DBMS_OUTPUT.put_line ('ln_final_total --> ' || ln_total);
END;
/

Answer 2

Indeed there's no problem with the logic, but change the style such as
if HEADER_ID is column of numeric type, then remove the preceding
zero of 0123, otherwise quote that as '0123'
INTO clause cannot be used for a cursor definition. Eg. get rid of
INTO ln_total. So remove that local variable
Convert SUM (qty * price * rate) within the query of the cursor to
ROUND(SUM (qty * price * rate),2). So, get rid of ln_final_total
local variable
Therefore, you can use the below code block
DECLARE
ln_grand_total NUMBER(10,2);
CURSOR E1 IS
SELECT ROUND( SUM(qty * price * rate), 2)
FROM maximo.po_lines pl
JOIN maximo.po_headers ph
ON pl.HEADER_ID = ph.HEADER_ID
WHERE ph.HEADER_ID = '0123';
BEGIN
OPEN E1;
FETCH E1
INTO ln_grand_total;
CLOSE E1;
DBMS_OUTPUT.PUT_LINE('ln_grand_total --> ' || ln_grand_total);
END;
/