Sql Sql Server T Sql Rounding

How to `Truncate` Decimal Places in SQL Server Without Rounding

When working with decimal values in SQL Server, you might sometimes find the need to manage the number of decimal places in your data. The typical ROUND function rounds the number, which may not be suitable for all scenarios. In this blog post, we will explore how to truncate decimal places in SQL Server without rounding them.

The Problem: Rounding vs. Truncating

Imagine you have a decimal value like 123.456, and you want to keep it to two decimal places. Using the standard rounding methods in SQL Server will automatically adjust the value to 123.46. However, there are situations where you just want to drop the extra decimals, resulting in 123.45 instead. This is where truncation becomes essential.

Let’s take a quick look at a sample value:

DECLARE @value DECIMAL(18,2);
SET @value = 123.456;

After executing this code with standard rounding, @value would become 123.46. But what if you wish to keep it as 123.45?

The Solution: Using the ROUND Function

SQL Server provides a powerful ROUND function that can help you truncate decimal places. The function requires three parameters:

number: This is the decimal value you want to truncate.
decimals: Specify how many decimal places you want to keep.
operation: This is optional. Set this parameter to 0 to round the result or to any other value (for example, 1) to truncate it.

Example Usage

Here’s how you can use the ROUND function effectively:

SELECT ROUND(123.456, 2, 1);

In this case, using 1 as the third parameter will truncate the value to 123.45, instead of rounding it.

Compatibility

The ROUND function with truncating capabilities works in the following environments:

SQL Server (starting with version 2008)
Azure SQL Database
Azure SQL Data Warehouse
Parallel Data Warehouse

For additional details, you can refer to the W3Schools SQL Server ROUND documentation.

Conclusion

By using the ROUND function with the appropriate parameters, you can easily truncate decimal places in SQL Server without rounding your values. This method ensures you have precise control over your data presentation, maintaining the integrity and accuracy required for your specific project needs.