Oracle convert number to float tips

Question:  I have column value of 00000000399 and I need to convert this to a floating point number like 3.99.  How do I convert a number column to a floating point number?

Answer:  Oracle has several ways to convert a number (or a string!) to a floating pint number.  The ideal of a floating point number is a DISPLAY issue and you convert it at select time.  The Oracle documentation shows these examples for table column datatypes and displayed values:

Actual Data	Specified As	Stored As
123.89	NUMBER	123.89
123.89	NUMBER(3)	124
123.89	NUMBER(6,2)	123.89
123.89	NUMBER(6,1)	123.9
123.89	NUMBER(3)	exceeds precision
123.89	NUMBER(4,2)	exceeds precision
123.89	NUMBER(6,-2)	100
.01234	NUMBER(4,5)	.01234
.00012	NUMBER(4,5)	.00012
.000127	NUMBER(4,5)	.00013
.0000012	NUMBER(2,7)	.0000012
.00000123	NUMBER(2,7)	.0000012
1.2e-4	NUMBER(2,5)	0.00012
1.2e-5	NUMBER(2,5)	0.00001

Oracle number data types and floating points (Source: Oracle Corporation Documentation)

Oracle string to number conversion:

Consider a table with a character string, containing a number:

create table
   mytab
(numcol varchar2);

insert into mytab values ('12345.67');

In SQL*Plus, Oracle will automatically convert a string to a floating point number (called "implicit conversion") or a number data type to a float display using the "column" and "format" clauses:

column numcol format 9999.99

select to_number(numcol) from mytab;

You can also convert a string datatype to a floating point number using Oracle built-in functions:

select
   to_binary_double(numcol) binary_double,
   to_binary_float(numcol)  binary_float_number,
   to_number(numcol)        number_datatype
from mytab;

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