


How to Efficiently Remove the Time Component from a DateTime Value in SQL Server?
Optimizing Datetime Data: Removing the Time Component in SQL Server
The Challenge:
Working with datetime
fields often requires isolating the date portion, excluding the time. This article explores the most efficient method for this common SQL Server task.
Recommended Approach:
After comparing different techniques, the most efficient and flexible solution is:
SELECT DATEADD(dd, DATEDIFF(dd, 0, GETDATE()), 0)
Performance Analysis:
This method consistently demonstrates superior performance, especially with large datasets. Its inherent flexibility extends to calculating other date-related values (e.g., determining the first day of the month).
Alternative Methods and Limitations:
Converting to varchar
using CONVERT(char(11), GETDATE(), 113)
offers acceptable performance in some cases, but carries potential risks. Language/date format inconsistencies can arise due to the varchar
conversion. Furthermore, this method lacks the adaptability of the DATEADD
/DATEDIFF
approach.
SQL Server 2008 and Beyond:
SQL Server 2008 and later versions provide a streamlined alternative: direct casting to date
. For example: CAST(GETDATE() AS DATE)
. This simplifies the process significantly.
Indexing and Performance Considerations:
Using functions or CAST
operations within WHERE
clauses can negatively impact index utilization. Careful planning is essential to maintain optimal query performance.
Handling datetime2
:
The same principles apply to datetime2
(introduced in SQL Server 2008 and enhanced in SQL Server 2019). Here's an example:
DECLARE @datetime2value datetime2 = '02180912 11:45'; -- Year 0218 for demonstration within datetime2 range DECLARE @datetime2epoch datetime2 = '19000101'; SELECT DATEADD(dd, DATEDIFF(dd, @datetime2epoch, @datetime2value), @datetime2epoch);
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