Oracle FLOAT Data Type

1.    The FLOAT data type is a subtype of NUMBER.

2.     It can be specified with or without precision, which has the same definition it has for NUMBER and can range from 1 to 126.

3.    Scale cannot be specified but is interpreted from the data.

4.    Each FLOAT value requires from 1 to 22 bytes.

To convert from binary to decimal precision, multiply n 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.

The difference between NUMBER and FLOAT is best illustrated by example. In the following example the same values are inserted into NUMBER and FLOAT columns:

Example:

CREATE TABLE test (col1 NUMBER(5,2), col2 FLOAT(5));

INSERT INTO test VALUES (1.23, 1.23);

INSERT INTO test VALUES (7.89, 7.89);

INSERT INTO test VALUES (12.79, 12.79);

INSERT INTO test VALUES (123.45, 123.45);

 SELECT * FROM test;

 

      COL1       COL2

---------- ----------

      1.23        1.2

      7.89        7.9

     12.79         13

    123.45        120

The FLOAT value returned cannot exceed 5 binary digits. The largest decimal number that can be represented by 5 binary digits is 31. The last row contains decimal values that exceed 31.

Therefore, the FLOAT value must be truncated so that its significant digits do not require more than 5 binary digits. Thus 123.45 is rounded to 120, which has only two significant decimal digits, requiring only 4 binary digits.

Oracle Database uses the Oracle FLOAT data type internally when converting ANSI FLOAT data. Oracle FLOAT is available for you to use, but Oracle recommends that you use the BINARY_FLOAT and BINARY_DOUBLE data types instead, as they are more robust.

 

CREATE TABLE test (col1 NUMBER(5,2), col2 FLOAT(5)); INSERT INTO test VALUES (1.23, 1.23); INSERT INTO test VALUES (7.89, 7.89); INSERT INTO test VALUES (12.79, 12.79); INSERT INTO test VALUES (123.45, 123.45);