oracle定义sql函数

求助oracle定义sql函数
create or replace function getTerm(username_new varchar2(32))
return varchar2(10)
as
begin
     result varchar2(10);
     term number:=1;
 yearCode varchar2(10):=substr(username_new,4,2);
 semesterCode varchar2(10):=substr(username_new,6,1);
 year number:=convert(number,yearCode);
 currentdate date(7):=TO_DATE(to_char(getdate(),'YYYY-MM-DD'),'YYYY-MM-DD');
 currentyear number:=convert(number,to_char(currentdate,'yyyy'));
 lastyear number:=0;
 d date(7):=TO_DATE(to_char(currentdate,'YYYY')+'-'+'03-16','YYYY-MM-DD');
 newTermStartDate date(7);
 lastTermEndDate date(7);
 if currentdate<d then
     lastyear:=1;
     end if;
 if lastyear=1 then
 currentyear:=currentyear-1;
     end if;
     term:=(currentyear-year)*2;
     newTermStartDate:=TO_DATE(to_char(currentdate,'YYYY')+'-09-16','YYYY-MM-DD');
     lastTermEndDate:=TO_DATE(to_char(currentdate,'YYYY')+'-03-16','YYYY-MM-DD');
 if currentdate<newTermStartDate then
    if currentdate>lastTermEndDate then
   term:=term+1;
end if;
 else
term:=term+2;
 end if;
 if semesterCode=2 then
term:=term-1;
 end if;
 result:=convert(varchar2(10),term);
 return result;
end getTerm;
这是我写的sql函数
下面是错误报告：
[Err] ORA-24344: success with compilation error

[Err] create or replace function getTerm(username_new varchar2(32))
return varchar2(10)
as
begin
     result varchar2(10);
     term number:=1;
 yearCode varchar2(10):=substr(username_new,4,2);
 semesterCode varchar2(10):=substr(username_new,6,1);
 year number:=convert(number,yearCode);
 currentdate date(7):=TO_DATE(to_char(getdate(),'YYYY-MM-DD'),'YYYY-MM-DD');
 currentyear number:=convert(number,to_char(currentdate,'yyyy'));
 lastyear number:=0;
 d date(7):=TO_DATE(to_char(currentdate,'YYYY')+'-'+'03-16','YYYY-MM-DD');
 newTermStartDate date(7);
 lastTermEndDate date(7);
 if currentdate<d then
     lastyear:=1;
     end if;
[Err] ORA-00900: invalid SQL statement

[Err] if lastyear=1 then
 currentyear:=currentyear-1
[Err] ORA-00900: invalid SQL statement

[Err] end if
[Err] ORA-00900: invalid SQL statement

[Err] term:=(currentyear-year)*2
[Err] ORA-00900: invalid SQL statement

[Err] newTermStartDate:=TO_DATE(to_char(currentdate,'YYYY')+'-09-16','YYYY-MM-DD')
[Err] ORA-00900: invalid SQL statement

[Err] lastTermEndDate:=TO_DATE(to_char(currentdate,'YYYY')+'-03-16','YYYY-MM-DD')
[Err] ORA-00900: invalid SQL statement

[Err] if currentdate<newTermStartDate then
    if currentdate>lastTermEndDate then
   term:=term+1
[Err] ORA-00900: invalid SQL statement

[Err] end if
[Err] ORA-00900: invalid SQL statement