Order BY in Subquery : Missing right parenthese - sql

Question

I try to update 2 columns using a subquery with a specific order so the query is like that:
UPDATE myTable TAO
SET (TAO.BASE_AMT,TAO.TAX_CD_VAT_PCT) = (SELECT SUM(decode(TAX_CD_VAT_PCT,0,0,d.monetary_amount))
, MAX (D.TAX_CD_VAT_PCT)
FROM source1 w
, source2 d
WHERE 1=1
-- Some conditions
GROUP BY d.business_unit, d.voucher_id
ORDER BY d.business_unit, d.voucher_id);
Why am I getting:
ORA-00907: missing right parenthesis
EDIT 1
the query with all conditions :
UPDATE myTable TAO
SET (TAO.BASE_AMT,TAO.TAX_CD_VAT_PCT) = (
SELECT SUM(decode(TAX_CD_VAT_PCT
, 0
, 0
,d.monetary_amount))
, MAX (D.TAX_CD_VAT_PCT)
FROM source1 w
, source2 d
WHERE w.business_unit = TAO.BUSINESS_UNIT
AND d.business_unit = w.business_unit
AND d.voucher_id = w.voucher_id
AND d.VOUCHER_LINE_NUM = w.VOUCHER_LINE_NUM
AND d.VOUCHER_ID = TAO.VOUCHER_ID
GROUP BY d.business_unit, d.voucher_id
ORDER BY d.business_unit, d.voucher_id )

Answer 1

You would appear to want a correlated subquery, because your subquery can return multiple rows.
You don't provide a table layout, but I would expect:
UPDATE myTable TAO
SET (BASE_AMT, TAX_CD_VAT_PCT) =
(SELECT SUM(d.monetary_amount), -- the DECODE does nothing
MAX(D.TAX_CD_VAT_PCT)
FROM source1 w JOIN -- ALWAYS use proper, explicit, standard JOIN syntax
source2 d
ON . . .
WHERE . . . AND
d.business_unit = TAO.business_unit AND
d.voucher_id = TAO.voucher_id
);
Your code is filled with anachronisms and bad practices:
The DECODE() does nothing. If it did, you should use CASE expressions instead.
Commas in JOIN clauses have been obsolete for over fifteen years. Use proper, explicit, standard JOIN syntax.
The ORDER BY in the subquery does nothing.

Answer 2

Subquery have group by clause which can return multiple rows.
Update query cannot take list of values to update.
So, for every unique combination of d.business_unit, d.voucher_id, there will be one row even if you did not select those columns in the inner query.
Also, assuming it returns only one row, you are missing where clause for update query. Only where clause I can see is in subquery.