Different treatments limit precision for each type: precision for NUMERIC columns is exactly “as declared”, while DECIMAL columns accepts numbers whose precision is at least equal to what was declared.

For instance, NUMERIC(4, 2) defines a number consisting altogether of four digits, including two digits after the decimal point; that is, it can have up to two digits before the point and no more than two digits after the point. If the number 3.1415 is written to a column with this data type definition, the value of 3.14 will be saved in the NUMERIC(4, 2) column.

The form of declaration for fixed-point data, for instance, NUMERIC(p, s), is common to both types. It is important to realise that the s argument in this template is scale, rather than “a count of digits after the decimal point”. Understanding the mechanism for storing and retrieving fixed-point data should help to visualise why: for storage, the number is multiplied by 10s (10 to the power of s), converting it to an integer; when read, the integer is converted back.

The method of storing fixed-point data in the DBMS depends on several factors: declared precision, database dialect, declaration type.

3.3.1.

Data Declaration Format

Storage Examples

Further to the explanation above, the DBMS will store NUMERIC data according the declared precision and scale. Some more examples are:

3.3.2. DECIMAL

Data Declaration Format

Storage Examples

The storage format in the database for DECIMAL is very similar to NUMERIC, with some differences that are easier to observe with the help of some more examples: