SQL Server Date Cast

Hello Dev, if you are in the process of working with date functions in SQL Server, you might come across the need to cast a date value to a specific data type. This might be required when you need to compare or calculate date values with other data types such as strings or integers. In this article, we will explore the various ways in which you can cast a date value in SQL Server.

Casting Date to Date Time Data Types

The most common way to cast a date in SQL Server is to convert it to a date time data type. This conversion can be done using the CONVERT function, which takes the date value as its first argument and the target data type as the second argument. Here is an example:

Date Value	Converted Value
2020-01-01	2020-01-01 00:00:00.000
2020-01-01 15:30:00	2020-01-01 15:30:00.000

As you can see from the table, the CONVERT function returns the date value in the specified date time format. It is important to note that the date time format depends on the language and date format settings of your SQL Server instance.

Using CAST function to convert date to datetime

Besides CONVERT function, SQL Server also provides the CAST function to convert a date to a date time data type. This function is similar to the CONVERT function, but uses a different syntax. Here is an example:

Date Value	Converted Value
2020-01-01	2020-01-01 00:00:00
2020-01-01 15:30:00	2020-01-01 15:30:00

The CAST function returns the date value in the specified date time format without the milliseconds.

Using a Custom Date Time Format

It is also possible to cast a date to a custom date time format. This can be useful when you need to extract specific components of a date value, such as the year or month. This can be achieved using the FORMAT function, which takes the date value as its first argument and a date time string as the second argument. Here is an example:

Date Value	Converted Value
2020-01-01	2020
2020-01-01 15:30:00	2020-01-01 15:30

The FORMAT function returns the date value in the specified date time format. You can use various date time string components to extract specific components of the date value.

Casting Date to Other Data Types

Besides casting a date to a date time data type, you might also need to cast it to other data types such as strings or integers. This can be useful when you need to compare or calculate date values with other data types. Here are some examples:

Casting Date to String

If you need to cast a date to a string data type, you can use the CONVERT function with a specific style. Here is an example:

Date Value	Converted Value
2020-01-01	Jan1 2020 12:00AM
2020-01-01 15:30:00	Jan1 20203:30PM

The CONVERT function returns the date value in the specified style. You can use various styles to format the date value in different ways.

Casting Date to Integer

If you need to cast a date to an integer data type, you can use the DATEDIFF function to calculate the number of days between two dates. Here is an example:

Date Value	Converted Value
2020-01-01	18262
2020-01-01 15:30:00	18262

The DATEDIFF function returns the number of days between the specified dates. You can use this value as an integer representation of the date value.

FAQ

Q: Can I cast a date to a float data type?

A: No, SQL Server does not allow casting a date to a float data type directly. However, you can use the DATEDIFF function to calculate the number of seconds or milliseconds between two dates, and then cast the result to a float data type.

Q: Can I use the CAST function to convert a date to a string?

A: Yes, you can use the CAST function with a specific style to convert a date to a string data type. However, the CONVERT function is more versatile and provides more options for formatting the date value.

Q: Can I use the FORMAT function to cast a date to an integer?

A: No, the FORMAT function returns a string data type. To cast a date to an integer data type, you should use the DATEDIFF function.

That’s it for this article on SQL Server Date Cast. We hope you found this information useful in your SQL Server development tasks. If you have any questions or comments, feel free to leave them below.