SQL & PL/SQL

UPDATE INV.MENU_LIST A
SET A.SRNO = (SELECT ROW_NUMBER() OVER (PARTITION BY GRP_CODE ORDER BY MENU_ID) FROM INV.MENU_LIST)
WHERE A.SRNO IS NULL;

Error starting at line : 12 in command -

UPDATE INV.MENU_LIST A

SET A.SRNO = (SELECT ROW_NUMBER() OVER (PARTITION BY GRP_CODE ORDER BY MENU_ID) FROM INV.MENU_LIST)

WHERE grp_code = 1

Error report -

ORA-01427: single-row subquery returns more than one row