oracle sql 日期yyyy-MM-dd字符串和timstamp类型相互转换

-- 日期yyyy-MM-dd字符串与timestamp类型转换
select to_char(startDate, 'yyyy-MM-dd') as start_date
  from start_date_info
 where startDate = to_timestamp('2015-09-24', 'yyyy-MM-dd hh24:mi:ssxff');