Datetime or Datetime2? Which SQL Server Data Type Should I Choose for Date and Time?

SQL Server 2008 Date and Time Data Type Selection: datetime vs. datetime2

When designing SQL Server 2008 and later databases, developers face a choice between datetime and datetime2 for storing date and time information. This guide clarifies the optimal selection based on best practices and technical considerations.

datetime vs. datetime2: Key Differences

Both data types store date and time values, but their capabilities differ significantly:

• Date Range and Precision: datetime2 boasts a broader date range (1 to 9999) compared to datetime (1753-1900) and offers millisecond to nanosecond precision, configurable by the user.
• Default Precision: datetime defaults to three decimal places for fractional seconds, while datetime2 defaults to seven.
• Customizable Precision: datetime2 allows users to define precision, optimizing storage and query performance.

Recommended Approach

Microsoft's MSDN documentation strongly recommends datetime2 for new applications. Its SQL standard compliance, improved portability, and enhanced precision (crucial for applications needing precise timekeeping or global time zone handling) make it the superior choice.

Storage Efficiency Considerations

Although datetime2 provides greater flexibility and accuracy, storage space is a factor. Users can mitigate this by specifying the necessary precision level, minimizing storage while retaining the required granularity.

Further Considerations

The following points warrant attention when deciding:

• Legacy System Compatibility: Existing systems or interoperability requirements might necessitate the use of datetime.
• Performance: While generally negligible, datetime2 might exhibit slightly higher overhead in specific scenarios. Performance testing is advisable for critical applications.

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