When working with data in SQL Server, it is often necessary to manipulate numbers and perform calculations. One common task is truncating decimal places, which involves rounding a number to a specified number of decimal places. This can be useful for displaying data in a more concise format or when dealing with large datasets that require precision.
To truncate decimal places in SQL Server, we can use the ROUND function. This function takes two parameters - the number to be rounded and the number of decimal places to round to. For example, if we have a number 3.14159 and we want to round it to two decimal places, we can use the ROUND function as follows:
ROUND(3.14159, 2)
This will result in the number 3.14 being returned. However, it is important to note that the ROUND function does not actually truncate the number, but instead rounds it to the specified number of decimal places. So, if we want to truly truncate the number, we need to use the FLOOR or CEILING function.
The FLOOR function returns the largest integer less than or equal to the specified number. So, if we use the FLOOR function on 3.14159, it will return 3. This effectively truncates the number to its integer value. However, if we want to truncate to a specific number of decimal places, we can combine the FLOOR function with the POWER function.
The POWER function takes two parameters - a number and an exponent. It returns the specified number raised to the specified exponent. So, if we use the POWER function with a number of 10 and an exponent of -2, we get 0.01. This can be used to truncate decimal places by using it as the multiplier in the FLOOR function.
For example, if we want to truncate 3.14159 to two decimal places, we can first use the POWER function to get 0.01 and then multiply it by the number we want to truncate. This results in 3.14159 * 0.01 = 0.0314159. Then, we can use the FLOOR function to truncate the number to its integer value, which is 0. Finally, we can divide the truncated number by the multiplier to get our final result of 0.03.
This may seem like a lot of steps, but fortunately, there is a shortcut. SQL Server provides a built-in function called TRUNCATE which does exactly what its name suggests - it truncates a number to a specified number of decimal places. So, if we use the TRUNCATE function on 3.14159 with a precision of 2, we get the same result as our previous example - 0.03.
It is important to note that the TRUNCATE function behaves differently than the ROUND function when it comes to negative numbers. While the ROUND function rounds negative numbers away from zero, the TRUNCATE function simply truncates the decimal places without any rounding. For example, if we use the TRUNCATE function on -3.14159 with a precision of 2, we get -3.14 instead of -3.15 like we would with the ROUND function.
In addition to the TRUNCATE function, SQL Server also provides the TRUNC function, which behaves similarly to the TRUNCATE function but only takes one parameter - the number to be truncated. This function is useful when we want to truncate a number to its integer value.
In conclusion, when working with numbers in SQL Server, we have several options for truncating decimal places. We can use the ROUND function for rounding, the FLOOR function for truncating to an integer value, and the TRUNCATE function for truncating to a specific number of decimal places. By understanding how these functions work, we can easily manipulate our data and display it in a format that is more useful and meaningful.
