SQL Server Convert Datetime to String

Hello Dev! It’s great to have you here. In this journal article, we will explore the process of converting datetime to string in SQL Server. This is a topic that is relevant to developers across different industries who want to manipulate and manage their data.

Understanding Datetime and String Conversion in SQL Server

In SQL Server, datetime is a data type that represents a date and time value. It is a very important data type that is used in various database applications. However, there are times when you may need to convert datetime to string in order to work with the data effectively. This is where the CONVERT function comes into play. The CONVERT function is used to convert the datetime value to a string.

Before we dive into the details of how to convert datetime to string in SQL Server, let’s take a look at why this conversion may be required. One reason could be that you want to format the output of a query. Another reason could be that you want to join two tables using a datetime column that has a different format. Whatever your reason may be, it’s important to understand the process of datetime to string conversion.

The Convert Function in SQL Server

The CONVERT function in SQL Server is used to convert an expression from one data type to another. In the context of datetime to string conversion, the CONVERT function is used to convert the datetime value to its string representation. The CONVERT function takes three parameters: the data type to which you want to convert, the expression you want to convert, and the style in which you want to display the output.

In order to convert datetime to string, the data type you want to convert to is ‘varchar’ or ‘nvarchar’. The expression you want to convert is the datetime value, and the style parameter determines how the output should be formatted. There are different style codes that can be used to format the output of the CONVERT function. We will discuss these style codes in more detail in the next section.

Style Codes for Date and Time Formats

When using the CONVERT function to convert datetime to string in SQL Server, you can use different style codes to format the output. These style codes determine how the output should be displayed in terms of date and time formats.

Style Code	Output Format
0	yyyy-mm-dd hh:mi:ss
1	mm/dd/yy
2	yy.mm.dd
3	dd/mm/yy
4	dd.mm.yy
5	dd-mm-yy
6	dd mmm yy
7	mmm dd, yy
8	hh:mi:ss
9	dd mon yyyy hh:mi:ss:mmm
10	mm-dd-yyyy
11	yyyy/mm/dd
12	yy/mm/dd
13	dd month yyyy
14	yyyy-mm-dd hh:mi:ss:mmm
20	yyyy-mm-dd hh:mi:ss (ODBC canonical)

Converting Datetime to String Using Convert Function

Now that we have a basic understanding of the CONVERT function in SQL Server and the different style codes for date and time formats, let’s look at how we can convert datetime to string using the CONVERT function.

The following syntax can be used to convert datetime to string:

CONVERT(varchar, datetimeColumn, styleCode)

Here, ‘datetimeColumn’ represents the name of the column that contains datetime values, and ‘styleCode’ represents the style code that you want to apply to format the output.

For example, if you have a table named ‘orders’ and you want to convert the ‘order_date’ column to string in the format ‘dd/mm/yyyy’, you can use the following query:

SELECT CONVERT(varchar, order_date, 103) AS order_date_string FROM orders

In the above query, the style code ‘103’ is used to format the output in the ‘dd/mm/yyyy’ format.

FAQs

1. What should I do if the output format that I want is not available in the style codes?

If the output format that you want is not available in the style codes, you can use the FORMAT function in SQL Server. The FORMAT function allows you to format date and time values in a custom format.

2. Can I convert string to datetime in SQL Server?

Yes, you can convert string to datetime in SQL Server using the CONVERT function. However, you need to make sure that the string is in a valid datetime format, otherwise the conversion will fail.

3. What are some best practices for datetime to string conversion in SQL Server?

Some best practices for datetime to string conversion in SQL Server include choosing the appropriate style code based on the desired output format, testing the conversion with sample data to ensure accuracy, and using the CONVERT function only when necessary to minimize performance impact.

4. Can I use the CONVERT function to convert other data types to string?

Yes, you can use the CONVERT function to convert other data types to string in SQL Server. The process is similar to converting datetime to string, except you need to choose the appropriate data type and style code for the conversion.

5. How do I handle null values when converting datetime to string?

When converting datetime to string in SQL Server, you may encounter null values in the datetime column. To handle null values, you can use the ISNULL or COALESCE function to replace null values with a default value before the conversion.