Oracle Floats vs Number

Question

I\'m seeing conflicting references in Oracles documentation. Is there any difference between how decimals are stored in a FLOAT and a NUMBER types in the database?

A

Answer 1

Bill's answer about Oracle's FLOAT is only correct to late version(say 11i), in Oracle 8i, the document says:

You can specify floating-point numbers with the form discussed in "NUMBER Datatype". Oracle also supports the ANSI datatype FLOAT. You can specify this datatype using one of these syntactic forms:

FLOAT specifies a floating-point number with decimal precision 38, or binary precision 126. FLOAT(b) specifies a floating-point number with binary precision b. The precision b can range from 1 to 126. To convert from binary to decimal precision, multiply b by 0.30103. To convert from decimal to binary precision, multiply the decimal precision by 3.32193. The maximum of 126 digits of binary precision is roughly equivalent to 38 digits of decimal precision.

It sounds like a Quadruple precision(126 binary precision). If I am not mistaken, IEEE754 only requires b = 2, p = 24 for single precision and p = 53 for double precision. The differences between 8i an 11i caused a lot of confusion when I was looking into a conversion plan between Oracle and PostgreSQL.