oracle字符转time

SELECT
to_char(a.TIME,‘HH24’) AS time,
a.dvalue AS dvalue,
a.cindex AS cindex,
b.sid AS sid
FROM table1 a, table2 b
WHERE a.type_id = 2
AND a.info_id = b.id
AND time >= to_timestamp(‘2018-08-01 00:00:00’,‘yyyy-mm-dd hh24:mi:ss’)
AND time <= to_timestamp(‘2018-08-01 23:59:59’,‘yyyy-mm-dd hh24:mi:ss’)
ORDER BY time