DateTime2 Vs DateTime in SQL SERVER

When dealing with date and time data types in SQL SERVER, there are two commonly used types – DateTime and DateTime2. While DateTime has been around for a long time, DateTime2 was introduced in SQL SERVER 2008. Both data types store date and time values, but there are some differences between them that developers should be aware of.

DateTime

DateTime is the older of the two data types and it is used to store dates and times in SQL SERVER with an accuracy of up to three milliseconds. The range of values supported by DateTime data type is from January 1, 1753, to December 31, 9999, with a default precision of 23. By default, the range of DateTime is from January 1, 1900, to June 6, 2079. This means that if you need to store a date that falls outside this range, you will need to use the DateTime2 data type.

DateTime2

DateTime2 is a newer data type that offers improved accuracy and a larger range of values. It was introduced in SQL SERVER 2008 and is the recommended data type for storing dates and times in SQL SERVER. The precision of DateTime2 data type is from 0 to 7, which makes it more flexible than the DateTime data type. The range of values supported by DateTime2 data type is from January, 1 0001 CE through December 31, 9999 CE, and from January 1, 0001 BC through December 31, 9999 BC. This data type is ideal for storing dates and times that are expected to fall outside the default range of the DateTime data type.

Differences between DateTime and DateTime2

While both DateTime and DateTime2 data types store date and time values, there are some significant differences between them:

  1. Precision – DateTime2 offers a higher level of precision than DateTime. While DateTime has a fixed precision of 23, DateTime2 allows for a precision of up to 7.

  2. Range – DateTime2 has a larger range of values than DateTime. While DateTime can store dates within a range of January 1, 1753, to December 31, 9999, DateTime2 can store dates from January 1, 0001 CE through December 31, 9999 CE, and from January 1, 0001 BC through December 31, 9999 BC.

  3. Storage – DateTime requires 8 bytes of storage while DateTime2 requires 6 to 8 bytes, depending on the precision of the data.

  4. Performance – DateTime2 is generally faster than DateTime when it comes to sorting and filtering large datasets. However, the difference in performance is usually minimal.

FAQs

Q. When should I use DateTime or DateTime2?

It is recommended to use DateTime2 instead of DateTime whenever possible, especially when you need to store dates and times that will fall outside the range supported by DateTime. DateTime2 also offers greater precision, which can be useful in certain scenarios. However, if you are working with an older system that only supports DateTime, you will need to use that.

Q. Can I convert DateTime to DateTime2 and vice versa?

Yes, you can convert DateTime to DateTime2 and vice versa using the CONVERT function. However, you need to be careful when converting from DateTime to DateTime2, as some data loss may occur if the value being converted falls outside the range supported by DateTime.

Q. Why does DateTime2 use less storage than DateTime?

DateTime2 uses less storage than DateTime because it has a smaller fixed part of the storage, which allows more bytes to be allocated for precision. In DateTime, the fixed part of the storage is 8 bytes, while in DateTime2, it is only 6 bytes. This means that more bytes are available for storing the date and time information, resulting in greater precision.

Q. Is there any backward compatibility issue when using DateTime2 instead of DateTime?

Yes, there may be backward compatibility issues when using DateTime2 instead of DateTime, especially if you are working with an older system that only supports DateTime. In such cases, you may need to convert the DateTime2 data type to DateTime before using it in the older system. Additionally, if you are upgrading an existing system to use DateTime2, you should test your system thoroughly to ensure that everything works as expected.

Q. Which data type should I use for storing time-zone aware times?

The recommended data type for storing time-zone aware times is DateTimeOffset. This data type allows you to store both a date and time value and a time-zone offset. This makes it easy to work with times that may be in different time zones, and ensures that the data is correctly adjusted for daylight saving time.

Conclusion

When it comes to storing date and time values in SQL SERVER, both DateTime and DateTime2 data types have their advantages and disadvantages. While DateTime is the older of the two, it has limited range and precision when compared to DateTime2. While DateTime2 offers greater precision and a larger range of values, it may cause backward compatibility issues in older systems. Ultimately, the choice between DateTime and DateTime2 will depend on the specific needs of your project.

Code blocks in HTML



CREATE TABLE SampleTable

(

  ID INT PRIMARY KEY IDENTITY(1,1),

  SampleDateTime DATETIME,

  SampleDateTime2 DATETIME2

)




INSERT INTO SampleTable (SampleDateTime, SampleDateTime2)

VALUES ('2022-01-01 02:03:04', '2022-01-01 02:03:04')

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