When storing and retrieving date and time values in a SQL database, you will often encounter the need to format these values in a way that is easily readable and understandable. In this tutorial, you will learn how to format datetime values in SQL using a variety of different formatting options.
Formatting Datetime Values as Strings
One common way to format datetime values in SQL is to convert them to strings using the CONVERT function. This function takes two arguments: the target data type and the input expression.
Here is an example of using the CONVERT function to format a datetime value as a string in the format yyyy-mm-dd hh:mm:ss:
SELECT CONVERT(VARCHAR(19), GETDATE(), 120);
The GETDATE() function returns the current date and time, and the VARCHAR(19) argument specifies that the output should be a string of length 19. The 120 argument specifies the format code for the desired output format.
Output: 2022-01-14 15:28:45
Formatting Datetime Values Using Format Functions
Another way to format datetime values in SQL is to use format functions. These functions take a datetime value as input and return a formatted string.
Here are some examples of format functions you can use to format datetime values:
1. FORMAT()
The FORMAT() function formats a datetime value with a specified format string. Here is an example of using the FORMAT() function to format a datetime value in the format yyyy-MM-dd HH:mm:ss:
SELECT FORMAT(GETDATE(), 'yyyy-MM-dd HH:mm:ss');
Output: 2022-01-14 15:28:45
2. CONVERT() with Style Codes
Another way to use the CONVERT function to format datetime values is to specify a style code instead of a target data type. Style codes specify a predefined format for the datetime value. Here is an example of using the CONVERT function with a style code to format a datetime value in the format yyyy-MM-dd HH:mm:ss:
SELECT CONVERT(VARCHAR(19), GETDATE(), 120);
Output: 2022-01-14 15:28:45
3. DATEPART()
The DATEPART() function extracts a specific part of a datetime value, such as the year, month, or day. Here is an example of using the DATEPART() function to extract the year from a datetime value:
SELECT DATEPART(YEAR, GETDATE());
Output: 2022
4. DATENAME()
The DATENAME() function returns the name of a specific part of a datetime value, such as the month name or day of the week. Here is an example of using the DATENAME() function to get the name of the month from a datetime value:
SELECT DATENAME(MONTH, GETDATE());
Output: January
Troubleshooting Tips
1. Invalid Input Values
If you are encountering errors when formatting datetime values, one possible cause is that your input values are not valid datetime values. Make sure that your input values are in the correct format and that they are valid datetime values.
2. Incorrect Format Codes
If you are using format codes to format datetime values, make sure that you are using the correct codes for the format you want. Refer to the documentation for your SQL database to find the correct format codes.
3. Different Time Zones
If you are working with datetime values in different time zones, you may need to adjust your formatting code to reflect the correct time zone. Make sure that you are using the correct time zone for your formatting code.
Conclusion
Formatting datetime values in SQL is an important task for making your data more readable and understandable. By using the CONVERT function and format functions like FORMAT(), DATEPART(), and DATENAME(), you can easily format datetime values in a variety of ways. Remember to check for invalid input values, incorrect format codes, and different time zones to troubleshoot any issues you may encounter.