Oracle時間を文字列に変換する方法

select * from Bt_Holiday whereto_char(Setting_DATE,'YYYY')=Substr('2015-03-00',1,4) AND
to_char(Setting_DATE,'MM')=Substr('2015-03-00',6, (instr('2015-03-00','-',1,2))-(instr('2015-03-00','-',1)+1))

Substr('2015-03-00',6, (instr('2015-03-00','-',1,2))-(instr('2015-03-00','-',1)+1))

select to_char(sysdate,'YYYY') from dual         输出为:2015
select to_char(sysdate,'MM') from dual         输出为:08
select to_date('2001-12-01','yyyy-mm-dd') from dual 输出为:2001/12/01
select sysdate from dual      输出为:2015/8/17 20:14:34
Substr('原始字符串','第几个字符开始','截取几个字符') 
select Substr('2015-03-00',1,4)  from dual   输出为:2015