• I am updating PREVIOUS_DAY_CLOSE column which contains DAY_CLOSE-1 values.
• I am using LAG() function to get PREVIOUS_DAY_CLOSE values. Its working fine.
• But updating the column with UPDATE and SELECT statement which is showing errors.

I have tried below queries and facing errors.

ORA-00928: missing SELECT keyword

with t1 as
(
SELECT datetime, LAG(CLOSE) OVER (ORDER BY datetime)AS PREVIOUS_CLOSE 
from stocks where SYMBOL='NASDAQ:IXIC'
)
update STOCKS
set PREVIOUS_CLOSE=t1.PREVIOUS_CLOSE
from t1
where t1.datetime=STOCKS.datetime;

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

update STOCKS
set PREVIOUS_CLOSE=
(SELECT LAG(CLOSE) OVER (ORDER BY datetime)AS PREVIOUS_CLOSE from STOCKS  where SYMBOL='NASDAQ:IXIC')
;