I need help figuring out how to calculate the time difference between two datetime columns in SQL Server. I have a table with timestamp data and I want to find out how many seconds passed between two specific times.
Let me give you an example of what I’m working with:
- First timestamp:
2010-03-15 08:45:12.250
- Second timestamp:
2010-03-15 08:45:28.180
I want to get the result as 15.930 seconds (the difference between these two times).
What’s the best SQL function or method to achieve this? I’ve been looking around but can’t find a clear solution that gives me the precise seconds with milliseconds included.
you can also use DATEDIFF with microseconds and divide by 1000000.0 - gives ya great precision. just run SELECT DATEDIFF(microsecond, starttime, endtime) / 1000000.0 and you’ll get decimel seconds. I’ve tested this tons of times and its solid for most cases.
Use DATEDIFF_BIG with CAST to obtain exact millisecond differences. The following query should work well:
SELECT CAST(DATEDIFF_BIG(MILLISECOND, ‘2010-03-15 08:45:12.250’, ‘2010-03-15 08:45:28.180’) AS FLOAT) / 1000.0 AS SecondsDifference
This will return exactly 15.930 seconds. I prefer DATEDIFF_BIG over the regular DATEDIFF because it handles larger time spans without overflow. Dividing by 1000.0 converts milliseconds to seconds while retaining decimal precision. Make sure to replace the hardcoded timestamps with your actual column names. This method is consistent across SQL Server versions and remains accurate for complex calculations.
interesting approaches! what happens with dates spanning multiple days tho? does the microsecond method handle month boundaries correctly? also curious about performance differences on larger datasets.