Efficient SQL Server datetime truncation: Removing time part

If you're working with dates in SQL Server, you may need to truncate the time part of a datetime value. There are several ways to do this, but some methods can be more efficient than others. Here are a few options:

├Źndice
  1. CAST or CONVERT
  2. DATEDIFF and DATEADD
  3. TRUNCATE and ROUND
  4. Conclusion

CAST or CONVERT

You can use the CAST or CONVERT functions to convert a datetime value to a date-only value. For example:

SELECT CAST(GETDATE() AS DATE)
SELECT CONVERT(DATE, GETDATE())

Both of these expressions return a date value without the time portion. However, they can be less efficient than other methods, especially if you're working with larger datasets.

DATEDIFF and DATEADD

You can also use the DATEDIFF and DATEADD functions to remove the time part of a datetime value. For example:

SELECT DATEADD(DAY, DATEDIFF(DAY, 0, GETDATE()), 0)

This expression uses DATEDIFF to calculate the number of days between January 1, 1900 (represented by 0) and the current datetime value. It then uses DATEADD to add that number of days to January 1, 1900, effectively truncating the time portion.

This method can be more efficient than using CAST or CONVERT, especially if you're working with large datasets and need to perform this operation frequently.

TRUNCATE and ROUND

Another option is to use the TRUNCATE or ROUND functions. For example:

SELECT TRUNCATE(CAST(GETDATE() AS FLOAT), 0)
SELECT ROUND(CAST(GETDATE() AS FLOAT), 0, 1)

Both of these expressions convert the datetime value to a float value, which represents the number of days since January 1, 1900. TRUNCATE simply removes the decimal portion of the float value, effectively truncating the time portion. ROUND rounds the float value to the nearest integer.

These methods can be more efficient than using DATEDIFF and DATEADD, but they may not be as intuitive for some developers.

Conclusion

When truncating the time part of a datetime value in SQL Server, there are several options to choose from. Using DATEDIFF and DATEADD can be efficient for large datasets, while TRUNCATE and ROUND can be more efficient but less intuitive. Experiment with different methods to find the one that works best for your situation.

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