Working with Dates and Times in SQL Server

When working with dates and times in SQL Server, it’s essential to understand the different formats and how to use them correctly. In this tutorial, we’ll explore the various ways to insert and query dates and times in SQL Server.

Understanding Date and Time Formats

SQL Server supports several date and time formats, including:

• YYYYMMDD: This is an unambiguous format that works for all languages.
• YYYY-MM-DD: This is the standard ANSI format, but it may not work for all languages.
• dd-mm-yy hh:mm:ss xm: This format requires the use of the CONVERT function with a specific style.

Inserting Dates and Times

To insert a date and time into a table, you can use the following syntax:

INSERT INTO table1 (approvaldate) VALUES ('20120618 10:34:09 AM');

This uses the YYYYMMDD format, which is unambiguous and works for all languages.

Alternatively, you can use the CONVERT function to convert a string to a datetime value:

INSERT INTO table1 (approvaldate) VALUES (CONVERT(datetime, '18-06-12 10:34:09 PM', 5));

In this example, the style 5 is used for Italian dates.

Using the ISO 8601 Format

The ISO 8601 format is a widely accepted standard for representing dates and times. It uses the format YYYY-MM-DDThh:mm:ss. This format is language-independent and works for all SQL languages:

INSERT INTO table1 (approvaldate) VALUES ('2012-06-18T10:34:09');

Querying Dates and Times

When querying dates and times, you can use the same formats as when inserting them. For example:

SELECT * FROM table1 WHERE approvaldate BETWEEN '2012-01-01' AND '2012-12-31';

This query uses the ISO 8601 format to filter the results.

Best Practices

When working with dates and times in SQL Server, it’s essential to follow best practices:

• Use the YYYYMMDD or ISO 8601 formats for inserting and querying dates and times.
• Avoid using ambiguous formats like dd-mm-yy hh:mm:ss xm.
• Use the CONVERT function when converting strings to datetime values.

By following these best practices, you can ensure that your date and time data is accurate and consistent across different languages and regions.

Additional Tips

When building queries in C# to run on SQL Server, use the Sortable "s" format specifier to pass dates in the ISO 8601 format:

string.Format("SELECT CONVERT(datetime2, '{0:s}'", DateTime.Now);

This ensures that the date is passed in a language-independent format.