Overview of SQL Server Rounding Functions – SQL Round, Ceiling and Floor

In SQL Server, there are several rounding functions that you can use to round numeric values to a specified precision. These functions allow you to control how the rounding is performed based on your requirements. Here’s an overview of the rounding functions available in SQL Server:

The SQL Server functions ROUND, FLOOR, and CEILING serve different purposes in rounding numeric values and have distinct behaviors:

Here’s a comparison of their behaviors:

ROUND:

Purpose: The ROUND function is used to round a numeric value to a specified length or precision. It rounds to the nearest value and can round both positive and negative numbers. If the value to be rounded is equidistant between two possible results, SQL Server rounds to the even number.

Syntax: ROUND(numeric_expression, length [, function]).

Example: SELECT ROUND(123.456, 2) AS rounded_value; returns 123.460.

FLOOR:

Purpose: The FLOOR function rounds a numeric value down to the nearest integer or to the next lower number. It always returns the largest integer less than or equal to the specified numeric value.

Syntax: FLOOR(numeric_expression).

Example: SELECT FLOOR(123.456) AS rounded_value; returns 123.

CEILING:

Purpose: The CEILING function rounds a numeric value up to the nearest integer or to the next higher number. It always returns the smallest integer greater than or equal to the specified numeric value.

Syntax: CEILING(numeric_expression).

Example: SELECT CEILING(123.456) AS rounded_value; returns 124.

Choose the appropriate function based on the specific rounding behavior needed for your own data type. If you need to round to a specific number of decimal places, use ROUND. If you need to always round down, use FLOOR, and if you need to always round up, use CEILING.

ROUND: The ROUND function rounds a numeric value to a specified length or precision. It rounds to the nearest value and supports rounding both positive and negative values. If the value to be rounded is equidistant between two possible results, SQL Server always rounds a number to the even number.

ROUND(numeric_expression, length [, function]) 

Example:

SELECT ROUND(123.456, 2) AS rounded_value; -- Output: 123.460 

CEILING: The CEILING function rounds a numeric value up to the nearest integer or to the next higher number.

CEILING(numeric_expression)
 

Example:

SELECT CEILING(123.456) AS rounded_value; -- Output: 124 

FLOOR: The FLOOR function rounds a numeric value down to the nearest integer or to the next lower to round the number off.

FLOOR(numeric_expression)
 

Example:

SELECT FLOOR(123.456) AS rounded_value; -- Output: 123 

ROUNDUP(numeric_expression, length)
 

SELECT ROUNDUP(123.456, 2) AS rounded_value; -- Output: 123.460 

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ROUNDDOWN: The ROUNDDOWN function rounds a numeric value down, toward zero, to the nearest multiple of significance.

ROUNDDOWN(numeric_expression, length)
 

Example:

SELECT ROUNDDOWN(123.456, 2) AS rounded_value; -- Output: 123.450 

These rounding functions provide flexibility in rounding numeric values to meet specific requirements in SQL Server queries. Choose the appropriate function based on the rounding behavior you need for your query data.

More Examples

Sure, here are some interesting examples of rounding in SQL Server:

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Round to Nearest Dollar:

SELECT ROUND(123.456, 0) AS rounded_value;

Output: 123 This rounds the value 123.456 to the nearest dollar.

Round to Nearest 10:

SELECT ROUND(123.456, -1) AS rounded_value;

Output: 120 This rounds the value 123.456 to the nearest 10.

Round Up to Nearest Integer:

SELECT CEILING(123.456) AS rounded_value;

Output: 124 This rounds up the value 123.456 to the nearest integer.

Round Down to Nearest Integer:

SELECT FLOOR(123.456) AS rounded_value;

Output: 123 This rounds down the value 123.456 to the nearest integer.

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Round to 2 Decimal Places:

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SELECT ROUND(123.456, 2) AS rounded_value;

Output: 123.460 This rounds the value 123.456 to 2 decimal places.

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Round to Nearest Half:

SELECT ROUND(123.456, 1) AS rounded_value;

Output: 123.500 This rounds the value 123.456 to the nearest half.

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Round to Nearest Thousand:

SELECT ROUND(12345.678, -3) AS rounded_value;

Output: 12000 This rounds the value 12345.678 to the nearest thousand.

These two table examples demonstrate various rounding scenarios in SQL Server, including rounding to integers, decimal places, significant digits, and multiples of powers of 10.

Using SQL ROUND() with Negative Precision

In SQL Server, you can use the ROUND() function with negative precision to round a numeric value to the nearest multiple of 10, 100, 1000, etc., corresponding to the specified precision. When the precision of input value is negative, the function rounds the value to the left of the decimal point.

Here’s an example:

SELECT ROUND(12345.678, -2) AS rounded_value;
 

In this example:

The numeric value 12345.678 is rounded to the nearest multiple of 100 (because the precision is -2).

The result will be 12300, which is the nearest multiple of 100 to 12345.678 when rounded to the left of the decimal point.

Similarly:

SELECT ROUND(12345.678, -1) AS rounded_value;
 

The numeric value 12345.678 is rounded to the nearest multiple of 10 (because the precision is -1).

The result will be 12350, which is the nearest multiple of 10 to 12345.678 when rounded to the left of the decimal point.

Using negative integer precision with the ROUND() function is useful when you need to round numbers to significant digits or adjust values to the nearest power of 10.