SQL Server Date Formatting: The Ultimate Guide for Devs

Greetings, Dev! If you’re working with SQL Server, you surely know the importance of date formatting. Perfectly formatted dates are not only important for data consistency and accuracy, but also play a critical role in reporting and analysis. This comprehensive guide will walk you through everything you need to know about SQL Server date formatting.

Understanding Date Formats

Before diving into SQL Server date formatting, let’s first understand what date formats are. Date formats are representations of dates in a specific order and pattern. Different countries and languages have their own set of date formats, for example, dd/mm/yyyy or mm/dd/yyyy.

SQL Server stores dates as a binary value, which is not human-readable. Therefore, to display it in a readable format, we need to format it using conversion functions. SQL Server supports a wide range of date formats, and this guide will help you understand and work with them.

Common Date Formats

Let’s start with the most commonly used date formats:

YYYY-MM-DD

The ISO standard date format uses the year, month, and day in this order, separated by hyphens. It is easily sortable and doesn’t cause confusion between countries that use different date formats. Use the CONVERT function with style 120 to format a date in this format:

Style	Output
120	2019-10-15

DD/MM/YYYY

The UK and many other countries use the day first, then month, then year format. Use the CONVERT function with style 103 to format a date in this format:

Style	Output
103	15/10/2019

MM/DD/YYYY

The US and many other countries use the month first, then day, then year format. Use the CONVERT function with style 101 to format a date in this format:

Style	Output
101	10/15/2019

Custom Date Formats

SQL Server also allows you to create custom date formats using the CONVERT function. The syntax for formatting a date in SQL Server is:

CONVERT(data_type(length), expression, style)

The data_type specifies the data type of the returned value, the expression is the date value you want to format, and the style specifies the format of the output. The following table lists some of the most commonly used styles:

Style	Output Format	Description
100	mon dd yyyy hh:miAM (or PM)	Default for datetime values in SQL Server
101	mm/dd/yyyy	USA date format
102	yyyy.mm.dd	ANSI date format
103	dd/mm/yyyy	UK date format
105	dd-mm-yyyy	Italian date format

Using Substring and Concatenation to Create Custom Formats

If the predefined formats do not meet your requirements, you can create your own date format by using the SUBSTRING and CONCATENATION functions. Here’s an example:

SELECT CONCAT(SUBSTRING(date_time, 1, 4),’/’, SUBSTRING(date_time, 5, 2), ‘/’, SUBSTRING(date_time, 7, 2)) AS MyDate FROM my_table

This SQL statement extracts the year, month, and day from a date column named date_time, and concatenates them with forward slashes to create a custom date format.

FAQs

How do I convert a string to a date in SQL Server?

You can use the CONVERT or CAST function to convert a string to a date in SQL Server. Here’s an example:

SELECT CONVERT(DATE, ‘2019-10-15’)

This statement converts the string ‘2019-10-15’ to a date value in SQL Server.

How do I extract the year from a date in SQL Server?

You can use the YEAR function to extract the year from a date in SQL Server. Here’s an example:

SELECT YEAR(date_column) AS Year FROM my_table

This statement extracts the year value from a date column named date_column in a table named my_table.

How do I add or subtract days from a date in SQL Server?

You can use the DATEADD function to add or subtract days from a date in SQL Server. Here’s an example:

SELECT DATEADD(day, 7, date_column) AS NewDate FROM my_table

This statement adds 7 days to a date column named date_column in a table named my_table.

That’s it for this comprehensive guide on SQL Server date formatting. We hope this article has helped you gain a better understanding of the different date formats, and how to format them in SQL Server. If you have any questions or comments, feel free to leave them below!