求2个函数：
1、把10进制数转成2进制字符串的函数，最好能指定转换长度。比如3转换成7位二进制字符串后为0000011。
2、从右边查找字符的函数，比如'0011000'查找'1'得到4，即右边那个1。
我不知道函数库中是否有这2个函数了，自己做怕效率低。
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1.
create or replace function to_base( p_dec in number, p_base in number )
return varchar2
is
l_str varchar2(255) default NULL;
l_num number default p_dec;
l_hex varchar2(16) default '0123456789ABCDEF';
begin
if ( p_dec is null or p_base is null )
then
return null;
end if;
if ( trunc(p_dec) <> p_dec OR p_dec < 0 ) then
raise PROGRAM_ERROR;
end if;
loop
l_str := substr( l_hex, mod(l_num,p_base)+1, 1 ) ¦ ¦ l_str;
l_num := trunc( l_num/p_base );
exit when ( l_num = 0 );
end loop;
return l_str;
end to_base;
/
create or replace function to_dec
( p_str in varchar2,
p_from_base in number default 16 ) return number
is
l_num number default 0;
l_hex varchar2(16) default '0123456789ABCDEF';
begin
if ( p_str is null or p_from_base is null )
then
return null;
end if;
for i in 1 .. length(p_str) loop
l_num := l_num * p_from_base + instr(l_hex,upper(substr(p_str,i,1)))-1;
end loop;
return l_num;
end to_dec;
/
show errors
create or replace function to_hex( p_dec in number ) return varchar2
is
begin
return to_base( p_dec, 16 );
end to_hex;
/
create or replace function to_bin( p_dec in number ) return varchar2
is
begin
return to_base( p_dec, 2 );
end to_bin;
/
create or replace function to_oct( p_dec in number ) return varchar2
is
begin
return to_base( p_dec, 8 );
end to_oct;
/
SQL> select to_bin( 123 ) bin, to_hex( 123 ) hex, to_oct( 123 ) oct from dual
2 /
BIN HEX OCT
--------------- --------------- ---------------
1111011 7B 173
SQL>
SQL> select to_dec( '1111011', 2 ) base2, to_dec( '7B' ) base16,
2 to_dec('173',8) base8
3 from dual
4 /
BASE2 BASE16 BASE8
---------- ---------- ----------
123 123 123
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2.
select instr('0011000','1',-1,1) from dual;
INSTR('0011000','1',-1,1)
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4
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