DateTime Convert in SQL Server

Hello Dev, have you ever been stuck in a situation where you had to convert a date or time value to a different format in SQL Server? If yes, then this article is for you. In this article, we will discuss different approaches to convert a datetime value in SQL Server. Let’s dive in!

Understanding DateTime Data Type

Before diving into datetime conversion, let’s first understand what datetime data type is. DateTime is a data type in SQL Server that represents the date and time values as a number of ticks since 00:00:00 UTC, January 1, 1970.

The datetime data type has a range of values from January 1, 1753, through December 31, 9999, and an accuracy of about 3.33 milliseconds.

Now that we know what datetime data type is, let’s explore different ways to convert a datetime value in SQL Server.

DateTime to String Conversion

One of the most common datetime conversions is from a datetime value to a string value. This conversion is useful when you want to display the datetime value in a specific format.

In SQL Server, you can use the CONVERT() function to convert a datetime value to a string. The syntax of the CONVERT() function is as follows:

Function	Description
CONVERT()	Converts an expression of one data type to another data type.

You can specify different styles to display the datetime value in a specific format. Here is an example:

SELECT CONVERT(varchar, GETDATE(), 101) AS [MM/DD/YYYY]SELECT CONVERT(varchar, GETDATE(), 102) AS [YYYY.MM.DD]SELECT CONVERT(varchar, GETDATE(), 103) AS [DD/MM/YYYY]SELECT CONVERT(varchar, GETDATE(), 104) AS [DD.MM.YYYY]SELECT CONVERT(varchar, GETDATE(), 105) AS [DD-MM-YYYY]

The output of the above query will display the datetime value in different formats based on the style specified in the CONVERT() function.

String to DateTime Conversion

Another common datetime conversion is from a string value to a datetime value. This conversion is useful when you want to insert a datetime value into a table or when you want to perform datetime arithmetic.

In SQL Server, you can use the CONVERT() function to convert a string value to a datetime value. The syntax of the CONVERT() function is as follows:

Function	Description
CONVERT()	Converts an expression of one data type to another data type.

You can specify different styles to convert the string value to a datetime value. Here is an example:

SELECT CONVERT(datetime, '2022-12-31 23:59:59', 120) AS [DateTime]SELECT CONVERT(datetime, '31/12/2022', 103) AS [DateTime]

The output of the above query will display a datetime value based on the style specified in the CONVERT() function.

DateTime Arithmetic

DateTime arithmetic can be performed using different SQL Server functions. The most commonly used functions are DATEADD(), DATEDIFF(), and GETDATE().

DATEADD() function adds or subtracts a specified time interval from a datetime value. Here is an example:

SELECT DATEADD(month, 1, GETDATE()) AS [NextMonth]SELECT DATEADD(day, -7, GETDATE()) AS [LastWeek]

The output of the above query will display a datetime value that adds or subtracts a specified time interval from the current datetime value.

DATEDIFF() function returns the difference between two datetime values in a specified time interval. Here is an example:

SELECT DATEDIFF(month, '2022-01-01', '2022-12-01') AS [MonthsDifference]SELECT DATEDIFF(day, '2022-01-01', '2022-12-31') AS [DaysDifference]

The output of the above query will display the difference between the two datetime values in a specified time interval.

GETDATE() function returns the current datetime value. Here is an example:

SELECT GETDATE() AS [CurrentDateTime]

The output of the above query will display the current datetime value.

Conclusion

DateTime conversions and arithmetic are essential functions in SQL Server. By understanding the different conversion and arithmetic functions, you can efficiently handle datetime values in SQL Server.

FAQs

Q. What is the difference between CONVERT() and CAST() functions in SQL Server?

A. CONVERT() function converts an expression of one data type to another data type with a specified format. CAST() function converts an expression of one data type to another data type without a specified format.

Q. Can I convert a datetime value to a date value in SQL Server?

A. Yes, you can use the CONVERT() function to convert a datetime value to a date value. The syntax of the CONVERT() function is as follows:

SELECT CONVERT(date, GETDATE()) AS [CurrentDate]