Floating Point Data Types

2. SQL Data Types : Data Types : Floating Point Data Types

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A floating point value is represented either as whole plus fractional digits (like decimal values) or as a mantissa plus an exponent.

The following is an example of the mantissa and exponent parts of floating point values:

There are two floating point data types:

• float4 (4-byte)

• float (8-byte)

A synonym for float4 is real. Synonyms for float are float8 and double precision.

Floating point numbers are stored in four or eight bytes. Internally, eight-byte numbers are rounded to fifteen decimal digits. The precision of four-byte numbers is processor dependent.

You can specify the minimum required binary precision (number of significant bits) for a floating point value using the following optional syntax:

float(n)

where n is a value from 0 to 53. Storage is allocated based on the precision that is specified, as follows:

Range of Binary Precision	Storage Allocated	Example
0 to 23	4-byte float	float(18) defines a floating point type with at least 18 binary digits of precision in the mantissa. A 4‑byte floating point field is allocated for it, which has 23 bits of precision.
24 to 53	8-byte float	float(41) defines a floating point type with at least 41 binary digits of precision in the mantissa. A 8‑byte floating point field is allocated for it, which has 53 bits of precision.

Floating point precision is not limited to the declared size.