Date Formats in SQL Server

Hello, Dev! Welcome to this informative article about date formats in SQL Server. As you may know, date and time values are an integral part of any database management system. In this article, we will explore various date and time data types supported by SQL Server, their syntax, and usage. We will also dive deep into the intricacies of date formatting and help you understand the different options available to you.

Date and Time Data Types

Before we jump into date formatting, let’s take a quick look at the different date and time data types supported by SQL Server:

Data Type	Storage Size	Accuracy
datetime	8 bytes	3.33 milliseconds
datetime2	6 to 8 bytes	100 nanoseconds to 1 nanosecond
date	3 bytes	1 day
time	3 to 5 bytes	100 nanoseconds to 1 nanosecond

As you can see, SQL Server provides a wide range of date and time data types to choose from, depending on your requirements. Let’s now look at how to declare and use these data types in SQL Server.

Declaring Date and Time Data Types

Declaring date and time data types in SQL Server is quite easy. Here’s the syntax:

DECLARE @myDateTime datetime = '2022-01-01 12:00:00'DECLARE @myDateTime2 datetime2(3) = '2022-01-01 12:00:00.123'DECLARE @myDate date = '2022-01-01'DECLARE @myTime time(3) = '12:00:00.123'

As you can see, you can declare a variable of a specific date and time data type and initialize it with a valid date and time value in the format ‘yyyy-mm-dd hh:mm:ss’.

Using Date and Time Data Types in SQL Queries

Once you have declared a date and time variable, you can use it in SQL queries. Here’s an example:

SELECT * FROM SalesOrders WHERE OrderDate >= @myDate

In the above example, we are selecting all sales orders where the order date is greater than or equal to the date value stored in the @myDate variable.

Date Formatting Options in SQL Server

SQL Server provides several built-in functions to format date and time values according to your specific requirements. Let’s explore some of these options in detail.

CONVERT Function

The CONVERT function is the most commonly used function to format date and time values in SQL Server. Here’s the syntax:

CONVERT(varchar(50), @myDateTime, 101)

In the above example, we are converting the @myDateTime value to a varchar data type using the 101 format style, which represents the date in the format ‘mm/dd/yyyy’.

Here are some other commonly used format styles:

Format Style	Output
100	mon dd yyyy hh:miAM (or PM)
101	mm/dd/yyyy
102	yyyy.mm.dd
103	dd/mm/yyyy

You can find a complete list of format styles in the SQL Server documentation.

FORMAT Function

The FORMAT function is another option to format date and time values in SQL Server. Here’s the syntax:

FORMAT(@myDateTime, 'yyyy/MM/dd')

In the above example, we are formatting the @myDateTime value in the ‘yyyy/MM/dd’ format.

DATEPART Function

The DATEPART function is used to extract specific parts of a date and time value. Here’s the syntax:

DATEPART(weekday, @myDate)

In the above example, we are extracting the weekday (1-7, Sunday-Saturday) from the @myDate value.

DATEADD Function

The DATEADD function is used to add or subtract a specified interval (year, month, day, hour, minute, second) from a date and time value. Here’s the syntax:

DATEADD(day, 7, @myDate)

In the above example, we are adding 7 days to the @myDate value.

FAQ

Q1. How do I change the default date format in SQL Server?

A1. You can change the default date format in SQL Server by changing the date format of the system user. Here’s the syntax:

EXEC sp_configure 'default language', 'us_english'RECONFIGURE WITH OVERRIDE

In the above example, we are changing the default language of the system user to ‘us_english’, which will change the default date format to ‘mm/dd/yyyy’.

Q2. How do I convert a string to a date value in SQL Server?

A2. You can use the CAST or CONVERT function to convert a string to a date value in SQL Server. Here’s the syntax:

SELECT * FROM SalesOrders WHERE OrderDate >= CONVERT(datetime, '2022-01-01', 101)

In the above example, we are converting the string ‘2022-01-01’ to a datetime value using the 101 format style and comparing it with the OrderDate column.

Q3. How do I find the difference between two dates in SQL Server?

A3. You can use the DATEDIFF function to find the difference between two dates in SQL Server. Here’s the syntax:

DATEDIFF(day, @myDate1, @myDate2)

In the above example, we are finding the difference in days between the @myDate1 and @myDate2 values.

Q4. How do I find the current date and time in SQL Server?

A4. You can use the GETDATE function to find the current date and time in SQL Server. Here’s the syntax:

SELECT GETDATE()

In the above example, we are selecting the current date and time.

Q5. How do I get the first day of the current month in SQL Server?

A5. You can use the DATEFROMPARTS function to get the first day of the current month in SQL Server. Here’s the syntax:

SELECT DATEFROMPARTS(YEAR(GETDATE()), MONTH(GETDATE()), 1)

In the above example, we are getting the first day of the current month.

Conclusion

That’s all for this article on date formats in SQL Server. We hope you found it helpful and informative. As you can see, there are several date and time data types, formatting options, and functions available in SQL Server to cater to your specific requirements. Feel free to experiment with different options and find the best one that suits your needs.