How Can I Truncate Decimal Places in SQL Server Without Rounding?

SQL Server Decimal Truncation: A Guide

Working with decimals in SQL Server often requires precise control over decimal places. Sometimes, you need to remove extra digits without the effect of rounding. While SQL Server's ROUND() function is primarily for rounding, it can also truncate.

To truncate, use the ROUND() function with a non-zero third argument. A zero in this position signifies rounding; any other value performs truncation.

Let's illustrate:

<code class="language-sql">DECLARE @value DECIMAL(18, 2);
SET @value = 123.456;</code>

Normally, @value would round to 123.46. To truncate:

<code class="language-sql">SELECT ROUND(@value, 2, 1);</code>

This returns 123.45, effectively truncating the extra decimal place.

Function Syntax and Parameters

The ROUND() function follows this structure:

<code class="language-sql">ROUND(numeric_expression, length [ ,function ])</code>

Here's a breakdown of the arguments:

Argument	Description
numeric_expression	The decimal value you want to truncate.
length	The desired precision (number of decimal places). Positive values specify decimal places to the right of the decimal point; negative values specify places to the left.
function	The operation type. 0 rounds; any non-zero value truncates.

Important Considerations

• The length parameter can be positive or negative. Positive values control decimal places to the right of the decimal point, while negative values affect digits to the left.
• The function parameter is optional; it defaults to 0 (rounding) if omitted.

This method provides a straightforward way to truncate decimal values in SQL Server without resorting to more complex workarounds.

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