TO_BINARY_FLOAT

Syntax

Description of the illustration to_binary_float.gif

Description of the illustration to_binary_float.eps

Purpose

TO_BINARY_FLOAT converts expr to a single-precision floating-point number.

• expr can be any expression that evaluates to a character string of type CHAR, VARCHAR2, NCHAR, or NVARCHAR2, a numeric value of type NUMBER, BINARY_FLOAT, or BINARY_DOUBLE, or null. If expr is BINARY_FLOAT, then the function returns expr. If expr evaluates to null, then the function returns null. Otherwise, the function converts expr to a BINARY_FLOAT value.

• The optional DEFAULT return_value ON CONVERSION ERROR clause allows you to specify the value returned by this function if an error occurs while converting expr to BINARY_FLOAT. This clause has no effect if an error occurs while evaluating expr. The return_value can be an expression or a bind variable, and must evaluate to a character string of type CHAR, VARCHAR2, NCHAR, or NVARCHAR2, a numeric value of type NUMBER, BINARY_FLOAT, or BINARY_DOUBLE, or null. The function converts return_value to BINARY_FLOAT in the same way it converts expr to BINARY_FLOAT. If return_value cannot be converted to BINARY_FLOAT, then the function returns an error.

• The optional ‘fmt’ and ‘nlsparam’ arguments serve the same purpose as for the TO_NUMBER function. If you specify these arguments, then expr and return_value, if specified, must each be a character string or null. If either is a character string, then the function uses the fmt and nlsparam arguments to convert the character string to a BINARY_FLOAT value.

If expr or return_value evaluate to the following character strings, then the function converts them as follows:

• The case-insensitive string ‘INF’ is converted to positive infinity.

• The case-insensitive string ‘-INF’ is converted to negative identity.

• The case-insensitive string ‘NaN’ is converted to NaN (not a number).

You cannot use a floating-point number format element (F, f, D, or d) in a character string expr.

Conversions from character strings or NUMBER to BINARY_FLOAT can be inexact, because the NUMBER and character types use decimal precision to represent the numeric value and BINARY_FLOAT uses binary precision.

Conversions from BINARY_DOUBLE to BINARY_FLOAT are inexact if the BINARY_DOUBLE value uses more bits of precision than supported by the BINARY_FLOAT.

See Also: TO_CHAR (number) and “Floating-Point Numbers”

Examples

Using table float_point_demo created for TO_BINARY_DOUBLE, the following example converts a value of data type NUMBER to a value of data type BINARY_FLOAT:

SELECT dec_num, TO_BINARY_FLOAT(dec_num)
  FROM float_point_demo;

   DEC_NUM TO_BINARY_FLOAT(DEC_NUM)
---------- ------------------------
   1234.56               1.235E+003

The following example returns the default value of 0 because the specified expression cannot be converted to a BINARY_FLOAT value:

SELECT TO_BINARY_FLOAT('2oo' DEFAULT 0 ON CONVERSION ERROR) "Value"
  FROM DUAL;

     Value
----------
         0