Conversion of datetime2 to datetime Data Type: Handling Out-of-Range Values

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Summary: Learn how to address the issue of out-of-range values when converting from the datetime2 data type to the datetime data type in SQL Server. Explore causes, solutions, and best practices.
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When working with SQL Server, one may encounter the error "Conversion of a datetime2 data type to a datetime data type results out-of-range value." This issue arises due to differences in the supported date ranges and precision of the datetime and datetime2 data types. Understanding these differences and knowing how to handle them is crucial for ensuring smooth data operations and avoiding errors.

Understanding datetime and datetime2 Data Types

datetime2 is an enhanced version of the datetime data type, introduced in SQL Server 2008. It offers a wider date range and greater precision:

datetime2: Supports dates from January 1, 0001, to December 31, 9999, with a time precision of up to 100 nanoseconds.

datetime: Supports dates from January 1, 1753, to December 31, 9999, with a time precision of 3.33 milliseconds.

The error occurs when attempting to convert a datetime2 value that falls outside the range supported by the datetime type, particularly those dates before January 1, 1753.

Causes of the Error

The primary cause of this error is having datetime2 values that are either:

Before January 1, 1753.

Of higher precision than datetime can handle.

Handling the Conversion

To handle this conversion without encountering errors, consider the following approaches:

Data Validation

Before converting, ensure that the datetime2 values fall within the valid range for datetime:

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Rows returned by this query contain dates that are not convertible to datetime. These need to be handled, possibly by adjusting the dates or excluding them from the conversion process.

Using TRY_CONVERT

The TRY_CONVERT function attempts the conversion and returns NULL for values that cannot be converted:

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This approach avoids the error and highlights problematic rows by returning NULL for out-of-range values.

Adjusting Out-of-Range Values

For dates that fall before the datetime range, consider adjusting them to a default minimum date, such as January 1, 1753:

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After adjustment, the conversion can proceed without errors.

Best Practices

To avoid similar issues in the future, follow these best practices:

Use datetime2 where possible: Given its broader range and higher precision, datetime2 is generally more suitable for new applications.

Consistent Data Types: Ensure consistent use of date and time data types across your database schema.

Validation on Insert/Update: Implement validation checks to prevent out-of-range values from being entered into your database.

Conclusion

Converting from datetime2 to datetime requires careful handling of out-of-range values. By understanding the differences between these data types and applying appropriate validation and conversion techniques, you can effectively manage and convert date and time data in SQL Server. Implementing best practices will help prevent such issues and ensure data integrity in your applications.