Round to first non-zero digit

Question

I am looking for a way to round floating point values the first n'th non-zero digit to the right of the decimal point.
for example if n = 1 then
round 0.01111 to 0.01
round 0.001111 to 0.001
round 0.0001111 to 0.0001
If I use the round argument then I need a way to determine what the parameter should be for the 2nd argument.
This requires me knowing how many zeros are to the right of the decimal point and before the first non-zero digit.
I have developed the following function to determine this. It is based on the binary search algorithm and will iterate at most 8 times.
CREATE OR REPLACE FUNCTION NUMBER_OF_LEADING_ZEROS(P_VALUE BINARY_DOUBLE) RETURN NUMBER IS
     L_MIN_ZEROS NUMBER;
     L_MAX_ZEROS NUMBER;
     L_MID NUMBER;
     L_ABS_VALUE BINARY_DOUBLE;
BEGIN
     L_MIN_ZEROS := 0;
     L_MAX_ZEROS := 130;
     L_ABS_VALUE := ABS(P_VALUE);
     IF L_ABS_VALUE IS NULL THEN
          RETURN NULL;
     ELSIF L_ABS_VALUE = BINARY_DOUBLE_NAN Or L_ABS_VALUE < POWER(10, -L_MAX_ZEROS) Then
          RETURN L_MAX_ZEROS;
     ELSIF L_ABS_VALUE >= 0.1 Then
          RETURN 0;
     END IF;
     LOOP
          L_MID := TRUNC((L_MIN_ZEROS + L_MAX_ZEROS) / 2);
          IF L_ABS_VALUE < POWER(10, -L_MID) And L_ABS_VALUE >= POWER(10, -(L_MID + 1)) Then
               RETURN L_MID;
          ELSIF L_ABS_VALUE < POWER(10, -(L_MID + 1)) Then
               L_MIN_ZEROS := L_MID + 1;
          ELSE
               L_MAX_ZEROS := L_MID - 1;
          End If;
     END LOOP;
END;If anyone can think of a more efficient way of doing this that would be great.

Answer 1

so small change to the above...
WITH tab AS
  ( SELECT 1.11111 col1 FROM dual
UNION ALL
   SELECT 0.001111 FROM dual
UNION ALL
   SELECT 0.0001111 FROM dual
UNION ALL
   SELECT 12.8518 FROM dual
--end of test data
SELECT ROUND(col1,case when LENGTH(regexp_substr(col1,'.0*'))=1 then 0 else LENGTH(regexp_substr(col1,'.0*')) end) col1,
  LENGTH(regexp_substr(col1,'.0*'))
   FROM tab;o/p of test when applied......
SQL> WITH tab AS
  2    ( SELECT 1.11111 col1 FROM dual
  3  UNION ALL
  4     SELECT 0.001111 FROM dual
  5  UNION ALL
  6     SELECT 0.0001111 FROM dual
  7  UNION ALL
  8     SELECT 12.8518 FROM dual
  9    )
10  --end of test data
11   SELECT ROUND(col1,case when LENGTH(regexp_substr(col1,'.0*'))=1 then 0 else LENGTH(regexp_subs
tr(col1,'.0*')) end) col1
12     FROM tab;
      COL1
         1
      .001
     .0001
        13Ravi Kumar