Understanding precision and scale of numeric in PostgreSQL

Precision and Scale

• Precision refers to the total number of significant digits in a number, both to the left and the right of the decimal point.

• Scale refers to the number of digits to the right of the decimal point.

Numeric Data Type

The NUMERIC data type in PostgreSQL can be defined with a specific precision and scale, using the syntax NUMERIC(precision, scale).

• precision (P): The maximum number of digits in the number.

• scale (S): The number of digits to the right of the decimal point.

Examples

• NUMERIC(5, 2) means the number can have up to 5 digits in total, with 2 digits to the right of the decimal point.

  • Valid values: 123.45, 12.34, 1.23

  • Invalid values: 1234.56 (too many digits), 123.456 (too many digits after the decimal point)

Implications

• Choosing the right precision and scale can help in saving storage space and ensuring data accuracy.

• If precision and scale are not specified, PostgreSQL will default to a precision of 131072 digits and a scale of 16383 digits, which can be unnecessarily large for most applications.

Understanding and correctly setting precision and scale in PostgreSQL ensures that your numeric data is stored efficiently and accurately. If you have more specific questions or need further clarification, feel free to ask!