How to Round HH:MM Time Values to the Nearest 15 Minutes in T-SQL?

Round HH:MM values ​​to the nearest 15 minute interval in T-SQL

Rounding to a specific interval is a common task when working with time values. This article explores an elegant T-SQL method for rounding HH:MM values ​​to the nearest 15-minute interval without relying on user-defined functions (UDFs) or case statements.

Solution:

The key to this technique is to use the datediff() and dateadd() functions to manipulate the date components while ignoring the seconds. We can determine the number of elapsed minutes by calculating the difference between the input date time and a fixed date with a time component of 00:00:00.

This value can then be divided by 15 to get the number of 15-minute intervals. The result is multiplied by 15 and added back to the fixed date using dateadd() to give a rounded time rounded to the nearest 15 minute interval.

Example query:

Consider the following example query:

<code class="language-sql">SELECT dateadd(minute, datediff(minute, '2023-01-01', GETDATE()) / 15 * 15, '2023-01-01') AS RoundedTime</code>

Replacing GETDATE() with your desired datetime value will return the rounded HH:MM value like this:

<code>| 输入时间 | 舍入时间 |
|---|---|
| 00:08:00 | 00:15:00 |
| 00:07:00 | 00:00:00 |
| 01:59:00 | 02:00:00 |</code>

Note:

This approach ensures consistent rounding behavior regardless of the input time value. It also avoids potential overflow errors when dealing with larger date ranges. Although it does not require a cast, an appropriately fixed date with a time component of 00:00:00 must be used as the basis for the calculation.

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