SQL Configuration and Conversion Function


An example of a configuration function in SQL is the @@SERVERNAME function. This function provides the name of the local server that's running SQL.


In SQL, most data conversions occur implicitly, without any user intervention.

To perform any conversions that can't be completed implicitly, you can use the CAST or CONVERT functions.

The CAST function syntax is simpler than the CONVERT function syntax, but is limited in what it can do.

In here, we use both the CAST and CONVERT functions to convert the datetime data type to the varchar data type.

The CAST function always uses the default style setting. For example, it will represent dates and times using the format YYYY-MM-DD.

The CONVERT function uses the date and time style you specify. In this case, 3 specifies the date format dd/mm/yy.

USE AdventureWorks2012
SELECT FirstName + ' ' + LastName + ' was hired on ' +
       CAST(HireDate AS varchar(20)) AS 'Cast',
       FirstName + ' ' + LastName + ' was hired on ' +
       CONVERT(varchar, HireDate, 3) AS 'Convert'
FROM Person.Person AS p
JOIN HumanResources.Employee AS e
ON p.BusinessEntityID = e.BusinessEntityID
David Hamiltion was hired on 2003-02-04David Hamiltion was hired on 04/02/03

Another example of a conversion function is the PARSE function. This function converts a string to a specified data type.

In the syntax for the function, you specify the string that must be converted, the AS keyword, and then the required data type. Optionally, you can also specify the culture in which the string value should be formatted. If you don't specify this, the language for the session is used.

If the string value can't be converted to a numeric, date, or time format, it will result in an error. You'll then need to use CAST or CONVERT for the conversion.

SELECT PARSE('Monday, 13 August 2012' AS datetime2 USING 'en-US') AS 'Date in English'
Date in English
2012-08-13 00:00:00.0000000