Oracle uses a standard, variable-length internal format for storing numbers. This internal format can maintain a precision of up to 38 digits.
The numeric datatype for Oracle is NUMBER. Declaring a column or variable as NUMBER will automatically provide a precision of 38 digits. The NUMBER datatype can also accept two qualifiers, as in:
column NUMBER( precision, scale )
The precision of the datatype is the total number of significant digits in the number. You can designate a precision for a number as any number of digits up to 38. If no value is declared for precision, Oracle will use a precision of 38. The scale represents the number of digits to the right of the decimal point. If no scale is specified, Oracle will use a scale of 0.
If you assign a negative number to the scale, Oracle will round the number up to the designated place to the left of the decimal point. For example, the following code snippet:
The NUMBER datatype is the only datatype that stores numeric values in Oracle. The ANSI datatypes of DECIMAL, NUMBER, INTEGER, INT, SMALLINT, FLOAT, DOUBLE PRECISION, and REAL are all stored in the NUMBER datatype. The language or product you’re using to access Oracle data may support these datatypes, but they’re all stored in a NUMBER datatype column.
With Oracle Database 10g, Oracle added support for the precision defined in the IEEE 754-1985 standard with the number datatypes of BINARY_FLOAT and BINARY_DOUBLE. Oracle Database 11g added support for the number datatype SIMPLE_INTEGER.
