Although some of the functions supported in Tableau have the same name as the functions you use in other applications or languages (SQL, for example), I caution you against assuming that it works the same way. There are functions that have the same name but will require different arguments, or return a different type, or both.

One example is the ISNULL function. In Tableau, the syntax of ISNULL is as follows:

ISNULL(expression)

This function in Tableau accepts a single argument and returns a Boolean value.

Transact-SQL (or T-SQL) has a similar function. However, the syntax in T-SQL is as follows:

ISNULL(check_expression, replacement_value)

In T-SQL, this function accepts two arguments and replaces the expression value if it is null. The return type is not a Boolean value. The function returns the same return type as the check_expression argument.

Support for regular expressions was introduced in Tableau V9. Regular expressions allow searching through patterns. This is quite powerful because sometimes the information is embedded in text, and it would be hard to search or extract otherwise.

Tableau also supports R expressions within Tableau calculated fields. The following is a list of functions that accept R expressions: