How to Choose the Right Precision and Scale for Storing Monetary Values in Decimal Columns?

Storing Monies in Decimal Columns: Precision and Scale Considerations

When storing monetary values in a database using a decimal column, determining the appropriate precision and scale can be crucial. While some may consider fixed-width char columns more efficient, decimal columns offer distinct advantages.

Precision and Scale

Precision refers to the total number of digits stored in the column, while scale determines the number of digits after the decimal point. For currencies that typically have four or five decimal places, a scale of 4 to 6 is usually sufficient.

A popular choice for monetary values is DECIMAL(19, 4), providing one additional decimal place for rounding purposes. This prevents truncation issues when storing values like 123.456 in a column with scale 4.

Determining Precision

While DECIMAL(19, 4) is a reasonable default, specific requirements may necessitate different settings. Consult experts in accounting and regulations to determine if industry-specific rules dictate a higher scale (e.g., DECIMAL(19, 6) for EU intra-state transfers).

Avoidance of SQL Server's MONEY Data Type

It's important to avoid using SQL Server's MONEY data type due to its known accuracy issues and rounding limitations.

Additional Considerations

Besides specifying precision and scale, consider the following:

• Store currency information in a separate account table.
• Perform conversion rate calculations in the application to maintain control over rounding issues.
• When using a float for conversion rates, ensure precision is not compromised by casting to decimal during calculations.

By carefully considering these factors, database designers can effectively store monetary values in decimal columns, ensuring accuracy and consistency while accommodating specific business requirements.

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