Mastering Date Format Conversions in SQL Server: Convert() vs Format()

Converting Date Formats in SQL Server: Using CONVERT() and FORMAT() Functions

Do you often find it difficult to manipulate and analyze dates in SQL Server? Do you get frustrated with the different date formats used in different countries around the world?

If the answer is yes, then you’re not alone!

One of the biggest challenges of working with dates in SQL Server is converting them to a different format. Fortunately, SQL Server provides two functions that can be used to convert dates: CONVERT() and FORMAT().

In this article, we’ll explore these two functions and examine how they can be used to convert date formats in SQL Server.

Using CONVERT() Function

The CONVERT() function is used to convert an expression from one data type to another. One of the most common uses of this function is to convert dates from one format to another.

The syntax of the CONVERT() function is as follows:

CONVERT (data_type [ (length)], expression, style)

The data_type parameter specifies the target data type to which the expression should be converted. The expression parameter specifies the value or expression to be converted.

The style parameter specifies the format of the date to be converted. The style parameter can be an integer or a string.

For example, let’s say that you have a table called “companies” that contains a column called “start_date” that stores the start date of each company. The data in this column is stored in a datetime format.

If you want to convert this date to a string format in the format of ‘yyyy/MM/dd’, you can use the following SQL statement:

SELECT CONVERT(NVARCHAR(10), start_date, 111) AS start_date FROM companies

In this SQL statement, the CONVERT() function is used to convert the start_date column to an NVARCHAR data type with a length of 10 characters. The 111 style code specifies that the date should be formatted as ‘yyyy/MM/dd’.

This way, the start_date value is now displayed in the desired format.

Using FORMAT() Function

The FORMAT() function is another useful function that can be used to format dates in SQL Server. The syntax of this function is as follows:

FORMAT (value, format)

The value parameter specifies the value or expression to be formatted.

The format parameter specifies the format of the date. The format parameter should be a valid .NET Framework string format.

For example, let’s say that you have the same “companies” table as earlier, and you want to convert the “start_date” column to a string in the format of ‘yyyy-MM-dd’. You can use the following SQL statement:

SELECT FORMAT(start_date, 'yyyy-MM-dd') AS start_date FROM companies

In this SQL statement, the FORMAT() function is used to format the start_date column to the ‘yyyy-MM-dd’ format.

This way, the start_date value is now displayed as a string, in the desired format.

Conclusion

In conclusion, converting date formats can be a challenging task when working with SQL Server. However, by using the CONVERT() and FORMAT() functions, you can easily convert dates from one format to another, making them easier to analyze and manipulate.

Whether you prefer using CONVERT() or FORMAT(), choose the one that’s most applicable and convenient for your needs. Happy coding!

3) Explanation and Usage of CONVERT() Function

The CONVERT() function in SQL Server is a powerful tool for transforming data types, including dates, from one format to another. It takes in three arguments: data_type, expression, and style.

The data_type argument specifies the target data type to which the expression should be converted. The most common data types used with CONVERT() are VARCHAR and NVARCHAR, which are used to store strings.

Other data types include DATE, TIME, and DATETIMEOFFSET. The expression argument specifies the value or expression to be converted, and the style argument specifies the format of the date to be converted.

In the example below, the CONVERT() function is used to convert the date value 2022-07-14 to a string in format ‘DD/MM/YYYY’:

SELECT CONVERT(VARCHAR(10), '2022-07-14', 103) AS converted_date;

In the syntax above, the first argument (VARCHAR) specifies the data type to which we will be converting the expression, the second argument (‘2022-07-14’) is the date value that will be converted, and the third argument (103) is the style code for the desired date format.

The third argument (style code) of the CONVERT() function specifies the format of the date to connect to.

The style code is a numeric expression that represents the conversion style. SQL Server provides a wide variety of style codes to choose from.

Some of the most popular date style codes are:

• 101: mm/dd/yyyy (default for US regions)
• 102: yyyy.mm.dd (ANSI)
• 103: dd/mm/yyyy (default for most European regions)
• 104: dd.mm.yyyy
• 105: dd-mm-yyyy
• 106: dd mon yyyy
• 107: Mon dd, yyyy
• 110: mm-dd-yyyy (US format)
• 111: yyyy/mm/dd
• 112: yyyymmdd (ISO format)
• 113: dd mon yyyy hh:mi:ss:mmm (European format with milliseconds)

These style codes can be used with the CONVERT() function to convert dates from one format to another.

4) Explanation and Usage of FORMAT() Function

The FORMAT() function in SQL Server is another tool that can be used to format dates and times. It takes in two arguments: value and format.

The value argument specifies the value or expression to be formatted, and the format argument specifies the format of the date or time. With FORMAT(), you have greater control over the format of your date or time values.

You can use custom format strings or built-in format strings.

Custom format strings are made up of one or more format specifiers.

A format specifier is a character in the format string that represents a part of the date or time value. For example, the format string “yyyy-MM-dd” specifies a four-digit year, followed by a dash, followed by a two-digit month, followed by another dash, followed by a two-digit day.

Here is an example that uses the FORMAT() function to format a date value of “2022-07-14” to string format ‘yyyy-MM-dd’:

SELECT FORMAT('2022-07-14', 'yyyy-MM-dd') AS formatted_date;

In the syntax above, the first argument (‘2022-07-14’) is the date value that will be formatted, and the second argument (‘yyyy-MM-dd’) represents the custom format string that specifies the desired date format.

The format string used in FORMAT() can include standard format specifiers, such as ‘d’ for the short date format, ‘t’ for the short time format, and ‘g’ for the short date/time format.

You can also use the format string to include separators, such as forward slashes, dashes, or colons, and to specify the order in which date or time components are displayed. The following table shows some of the most commonly used format specifiers for the FORMAT() function, along with their meanings:

These format specifiers can be combined to create many different date and time formats.

In conclusion, both the CONVERT() and FORMAT() functions are useful tools that can be used to format dates and times in SQL Server. The CONVERT() function is used to convert one data type to another, including dates and times, while the FORMAT() function is used to format dates and times.

With these functions, you can easily convert and format data to display it in the desired format.

5) Comparison of CONVERT() and FORMAT() Functions

While both the CONVERT() and FORMAT() functions can be used to format dates and times in SQL Server, they differ in some important ways. The CONVERT() function is primarily used to convert one data type to another, including dates and times.

It’s commonly used to convert date and time values from one format to another, as we saw in the previous section. With the CONVERT() function, you have a wide range of style codes to choose from when formatting dates, including both numeric and string values.

In contrast, the FORMAT() function is used primarily for formatting dates and times. It gives you greater control over the format of your date or time values and allows you to use custom format strings, which can include separators and specify the order in which date or time components are displayed.

Another important difference between the two functions is the version of SQL Server in which they were introduced. The CONVERT() function has been around since SQL Server 2000, so it’s compatible with all versions of SQL Server, including the latest version, SQL Server 2019.

On the other hand, the FORMAT() function was only introduced in SQL Server 2012, so if you’re working with an older version of SQL Server, you won’t be able to use it. When deciding which function to use for formatting dates and times, you should consider the version of SQL Server you’re working with.

If you’re using an older version of SQL Server, you’ll need to use the CONVERT() function to format dates and times. However, if you’re using SQL Server 2012 or a later version, you can choose between the CONVERT() and FORMAT() functions based on your requirements.

If you need more control over the format of your date and time values, the FORMAT() function may be the better choice for you. However, if you just need to convert one date format to another, the CONVERT() function is often easier and more efficient to use.

In terms of performance, both the CONVERT() and FORMAT() functions are efficient and don’t have a significant impact on query performance in most cases. However, it’s worth noting that the FORMAT() function can be slower than the CONVERT() function when processing large amounts of data.

This is because the FORMAT() function needs to parse the format string every time it’s called, whereas the CONVERT() function uses pre-defined style codes that don’t require parsing. In summary, both the CONVERT() and FORMAT() functions are useful for formatting dates and times in SQL Server, but they differ in their functionality and the versions of SQL Server in which they’re supported.

Choosing between these functions depends on your requirements and the version of SQL Server you’re using. If you just need to convert between date formats, the CONVERT() function may be easier to use, but if you need more control over the format of your date and time values, the FORMAT() function could be the better choice.

In conclusion, converting date formats is an essential skill when working with SQL Server. The CONVERT() and FORMAT() functions both offer powerful tools to help format dates and times in SQL Server depending on your needs.

While the CONVERT() function is useful for simply converting one date format to another, the FORMAT() function offers greater control and customization over the formatting of date and time values. Depending on the SQL Server version, one or both of these functions can be used, and it’s important to choose the one that best meets your requirements.

Being well-versed in these functions will greatly improve and simplify any date-related tasks in SQL Server.