Tableau 10 Business Intelligence Cookbook

Word of caution

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. ...