Understanding the Round Function in SQL Server

Hi Dev, if you’re a SQL Server developer or administrator, you must have heard about the round function. SQL Server offers various built-in functions to manipulate data, and the round function is one of them. This function helps you to round a decimal value to a specified number of decimal places. In this article, we’ll discuss different aspects of the round function, its syntax, usage, and examples. Let’s get started.

What is the Round Function?

The round function in SQL Server is used to round off the numerical value with the given precision. This function returns a rounded value based on the specified precision.

The syntax of the round function is:

Function	Description
ROUND(number, length, function)	number: The number to be rounded
	length: The number of decimal places to round off
	function: Type of round off to be performed

Parameters of the Round Function

Let’s discuss the parameters of the round function:

number

The number is the value to be rounded off. This can be a positive, negative, or zero value.

length

The length parameter is the number of decimal places to which the number should be rounded off. It can be a positive or negative value.

function

The function parameter is an optional argument that specifies the type of rounding off to be performed. There are four types of rounding available in SQL Server:

1. Round
2. Round up
3. Round down
4. Truncate

Let’s discuss each of these types in detail:

Round

The default function of the round function is “Round.” It rounds off the value to the specified number of decimal places. If the value after rounding off is exactly halfway between two numbers, it rounds to the nearest even number. For example, the number 1.5 rounds off to 2, but 2.5 rounds off to 2.

Round Up

The “Round Up” function of the round function rounds off the value to the next highest number. For example, the number 1.5 rounds off to 2, but 1.1 rounds off to 2.

Round Down

The “Round Down” function of the round function rounds off the value to the next lowest number. For example, the number 1.5 rounds off to 1, but 1.9 rounds off to 1.

Truncate

The “Truncate” function of the round function removes all the decimal places from the specified value. For example, if you truncate the value 1.9 to 1 decimal place, you’ll get 1.0.

Usage of the Round Function

The round function is mostly used in financial applications where precision is critical. Some of the common scenarios where the round function is used are:

1. Calculating the taxes on a financial transaction
2. Calculating the interest on a loan
3. Calculating the total amount on an invoice

Examples of the Round Function

Let’s discuss some examples of the round function:

Example 1:

Round the number 3.1416 to two decimal places:

Query	Result
SELECT ROUND(3.1416,2)	3.14

Example 2:

Round the number 3.1416 up to two decimal places:

Query	Result
SELECT ROUND(3.1416,2,1)	3.15

FAQ

Q. Can we use the round function with negative decimal places?

Yes, we can use the round function with negative decimal places to round off the value to the left of the decimal place. For example, if you use -2 decimal places on the round function for the number 123.45, it rounds off to 100.

Q. Does the round function support all data types?

No, the round function does not support all data types. It only supports numeric data types such as int, float, real, and decimal.

Q. What is the difference between rounding off and truncating?

The round function rounds off the number to the nearest specified decimal place, whereas the truncate function removes all the decimal places from the specified value.

Q. Can we use the round function with mathematical expressions?

Yes, we can use the round function with mathematical expressions to round off the result to a specified decimal place.

Q. Can we nest the round function in SQL Server?

Yes, we can nest the round function in SQL Server to perform multiple rounds on a decimal number.

Q. What are the other rounding functions available in SQL Server?

The other rounding functions available in SQL Server are:

1. Ceiling: rounds off the number to the next highest integer.
2. Floor: rounds off the number to the next lowest integer.

Conclusion

The round function in SQL Server is a simple yet powerful function that helps you round off decimal values to a specified precision level. With the examples and usage discussed in this article, you should be able to use the round function in your SQL Server queries effectively. Happy Querying!