Need to display only the date portion of a datetime or smalldatetime field in SQL Server without the time? This is a common task, and SQL Server offers several ways to achieve this cleanly and efficiently. This guide will walk you through the best methods, explaining their nuances and helping you choose the most appropriate technique for your specific situation.
Understanding the Problem
SQL Server's datetime and smalldatetime data types store both date and time information. Often, you only need the date. Displaying the time alongside the date can clutter reports or queries, making the data less readable. The key is to extract the date part, leaving the time component behind.
Methods to Display Only the Date
Here are the primary ways to achieve this, ranked in terms of best practice and efficiency:
1. Using CONVERT with Style 102
This is generally considered the most efficient and readable method. The CONVERT function allows you to specify a style to format the datetime value. Style 102 outputs the date in yyyy.mm.dd format. You can adjust the style for different date formats if needed (see the Style Codes section below).
SELECT CONVERT(VARCHAR(10), YourDateTimeField, 102) AS DateOnly
FROM YourTable;
Replace YourDateTimeField with the name of your datetime column and YourTable with the name of your table.
2. Using CAST to DATE
This method is straightforward and leverages SQL Server's DATE data type, introduced in SQL Server 2008. Casting directly to DATE effectively removes the time component. The output is a DATE data type, not a string.
SELECT CAST(YourDateTimeField AS DATE) AS DateOnly
FROM YourTable;
This is preferred if you need to perform further date calculations or comparisons; using the DATE data type directly is more efficient for date-specific operations compared to string manipulation.
3. Using FORMAT (SQL Server 2012 and later)
The FORMAT function provides more flexibility in formatting the output string, but it's generally less efficient than CONVERT for simple date extraction. Use this if you need highly customized date formatting beyond what's offered by CONVERT styles.
SELECT FORMAT(YourDateTimeField, 'yyyy-MM-dd') AS DateOnly
FROM YourTable;
Remember that FORMAT is less performant than CONVERT for large datasets; prioritize CONVERT or CAST whenever possible.
Style Codes for CONVERT (Important!)
The CONVERT function's style parameter allows for various date and time formats. Here are a few commonly used styles:
- 101: mm/dd/yyyy
- 102: yyyy.mm.dd
- 103: dd/mm/yyyy
- 104: dd.mm.yyyy
- 105: dd-mm-yyyy
- 106: dd mon yy
- 110: mm-dd-yyyy
- 111: yyyy/mm/dd
- 112: yyyyMMdd
Choose the style that best suits your regional settings and desired output format. Always consult the official SQL Server documentation for a complete list of style codes.
Choosing the Best Method
- For simple date extraction and optimal performance, use
CONVERTwith the appropriate style orCASTtoDATE. - For complex formatting needs (beyond the standard styles), consider
FORMAT(but be mindful of performance implications on large datasets). - If you plan on further date arithmetic, using
CASTtoDATEis the best choice, maintaining data type consistency and efficiency.
By applying these methods, you can efficiently extract and display only the date portion from your datetime fields in SQL Server, significantly improving the clarity and usability of your data. Remember to always choose the method best suited to your specific needs and data volume.
