请教oracle的字符函数，数学函数(与sqlserver的对照)

Question

如sqlserver中的：
Select @S=convert(varchar,@Fnumber))
Select @BillID=@Fheader+replace(str(@Fnumber,3),' ','0')在oracle 应该怎样写：

Answer 1

sqlserver                            oracle
   len                               length 
   datalength                        lengthb
   replace                           replace
   str()
   left                              
   rtrim                              rtrim
   charindex                         instrb --找出某个字符串的位置和字节数                                   instr  找出某个字符串的位置                      
.. null                               nvl
转换函数
sqlserver                            oracle
convert()                             to_char
......                                to_number 
                                      to_date
......

Answer 2

Select @S=convert(varchar,@Fnumber)) :
  S :=to_char(fnumber);
  或者： Select to_char(fnumber) into S from dual;
Select @BillID=@Fheader+replace(str(@Fnumber,3),' ','0')
  BillID :=Fheader || replace(to_char(Fnumber),' ','0')

Answer 3

感谢 welyngj， lianhg(lianhg) 
To: lianhg(lianhg) 
在Sqlserver中
Select @BillID=@Fheader+replace(str(@Fnumber,3),' ','0')
可以使得@Billid在前面自动添加00: 如：@Fnumber=1 则输出结果为001,Fnumber=10,则输出结果为010BillID :=Fheader || replace(to_char(Fnumber),' ','0')
但只能输出1,10

Answer 4

BillID :=Fheader || replace(to_char(Fnumber,'000'),' ','0')

Answer 5

还请教一个问题：
   有没有函数可以实现
     if Flen=1 then
       s:='0';
     else if flen=2 then 
       s:='00';
     else if flen=3 then
       s:='000';
     ..........
     end if;