Which Tableau function can be used to count distinct values in a field?

The COUNTD function in Tableau is specifically designed to count distinct values within a field. When you're working with datasets that contain duplicate entries and need to know how many unique values are present, COUNTD provides the necessary functionality. For example, if a customer database contained several records for the same customer, using COUNTD on the customer ID field would yield the number of unique customers rather than the total number of entries.

Other functions like COUNT simply tally the total number of entries, counting duplicates, while SUM adds numeric values together rather than counting distinct items. There is also no SUMD function in Tableau, clarifying that the use of COUNTD is the most appropriate for the requirement of counting distinct values. Thus, COUNTD is the correct choice for this specific task.