oracle日期的查询和插入

日期的查询：
 select to_char(hiredate,'yyyy-mm-dd') from emp; 日期的插入：
 insert into emp(hiredate) values(to_date('1990/02/2','yyyy/mm/dd'))；
 insert into emp(hiredate) values(to_date('1990/02/2','yyyy/mm/dd hh/MM/ss ms'));
 insert into emp(empno,hiredate) values(1110,to_date('1990/02/2 12:12:12','yyyy/mm/dd hh:mi:ss'));
 insert into emp(empno,hiredate) values(1111,to_timestamp('1990/02/2 12:12:12:666666','yyyy/mm/dd hh:mi:ss:ff'));