How to Convert EPOCH Time to Usable Dates in SQL Server for Comparison

Learn how to effectively convert EPOCH time to a datetime format in SQL Server and avoid common conversion errors.
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Understanding EPOCH Time and Its Importance in SQL Server

In today's data-driven world, working with timestamps is a critical skill. One common format you might encounter is EPOCH time, which represents the number of seconds since January 1, 1970. However, converting this raw numerical format into a usable date in SQL Server can sometimes lead to errors, particularly when you attempt to compare these dates with the current datetime.

In this guide, we will explore a specific scenario where you have a column named [last_run] that contains an EPOCH time value (for example, 1647644503000000000). We'll outline how to convert this EPOCH value into a readable date format and demonstrate how to effectively compare it with the current date without encountering conversion errors.

Converting EPOCH Time to a Usable Date

To convert EPOCH time to a SQL Server datetime format, you can use the DATEADD function in combination with some basic arithmetic operations. Here's how it works:

Divide the EPOCH value by 1,000,000,000 to convert from nanoseconds to seconds.

Adjust the time zone by subtracting the offset in seconds (in this case, 18000 seconds for EST).

Use DATEADD to add seconds to the base date of '1970-01-01'.

Here’s the SQL code that achieves this conversion:

[[See Video to Reveal this Text or Code Snippet]]

This SQL statement will convert the original EPOCH value to a readable date, which in the example returns something like Last_Backup = 2022-03-18 18:01:43.0000000.

Adding Date Difference Calculation

Once we've converted the EPOCH time to a usable date, you might want to calculate the difference between this date and the current date using DATEDIFF. Yet, you may encounter an error indicating that "Conversion failed when converting date and/or time from character string." This issue typically arises when the column names are mistakenly referenced as strings.

To avoid this error, you need to ensure that you're referring to the column correctly. One straightforward, albeit less efficient, approach is simply to repeat the computation for the converted date directly in your DATEDIFF calculation. Here’s how you can implement this in your SQL Server query:

[[See Video to Reveal this Text or Code Snippet]]

In this example:

The first line converts EPOCH time to a datetime.

The second line calculates the difference in days between the newly created Last_Backup date and the current date returned by GETDATE().

Conclusion

The ability to convert EPOCH time into a readable date format in SQL Server opens the door for a myriad of analysis opportunities. By understanding how to effectively perform these conversions and calculations, you can ensure your datetime comparisons are both accurate and error-free.

Next time you find yourself working with EPOCH time, remember these steps, and you’ll be on your way to mastering SQL Server datetime manipulations!