How Can I Achieve Custom Date/Time Formatting in SQL Server Using Functions?

Custom Date/Time Formatting in SQL Server

To meet specific formatting requirements for datetime fields, we will explore a solution that involves utilizing SQL Server's built-in functions and wrapping the logic in a function, rather than a stored procedure.

Converting to Custom Formats

To convert a datetime field to a format such as 'DDMMM', we can use the DATENAME function. For instance, the following code returns "14OCT" for the input '2008-10-12':

select DATENAME(day, @myTime) + SUBSTRING(UPPER(DATENAME(month, @myTime)), 0,4)

Similarly, to convert to a format like 'HHMMT', we can use the following logic:

select RIGHT('0' + CAST(DATEPART(hour, @myTime) AS VARCHAR(2)), 2) + RIGHT('0' + CAST(DATEPART(minute, @myTime) AS VARCHAR(2)), 2) + CASE WHEN DATEPART(hour, @myTime) < 12 THEN 'A' ELSE 'P' END

This will return "0119P" for the input '2008-10-12 13:19:12.0'.

Benefits of Using Functions

Utilizing functions instead of stored procedures provides several advantages:

• Improved performance: Functions are compiled once and stored in the server's memory, making them faster to execute than stored procedures.
• Reusability: Functions can be easily reused in different contexts, making code maintenance easier.
• Configurability: Functions can accept parameters, allowing for easy customization to meet specific requirements.

Additional Considerations

When working with dates, it's recommended to avoid character or string-based operations as they can impact performance. Instead, perform numerical calculations on dates as they are treated as floating-point values in SQL Server.

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