# ISMEMBEROF, USERNAME and other user functions

*Tableau Consultant Study Guide · Plan and Prepare Data Connections · Last updated November 3, 2026 · https://www.certifyforce.com/study-guide/tableau-consultant/plan-and-prepare-data-connections/ismemberof-username-and-other-user-functions*

Tell the group function ISMEMBEROF apart from the user functions USERNAME, FULLNAME, ISUSERNAME, ISFULLNAME and USERDOMAIN, know their literal-string, encoding, sign-in and session rules, and choose a group-based or data-driven security rule.

- Certification: Salesforce Tableau Consultant
- Exam section: Plan and Prepare Data Connections
- Study guide: https://www.certifyforce.com/study-guide/tableau-consultant

**Official exam objective:**

> Identify group functions versus user functions.

## What the exam expects

- Identify ISMEMBEROF as the group function and USERNAME, FULLNAME, ISUSERNAME, ISFULLNAME and USERDOMAIN as user functions, with what each returns.
- Apply the rules that break group tests: literal-string arguments, HTML URL encoding of special characters, NULL when not signed in, new sessions after membership changes.
- Predict which rows a filter that combines a user comparison and a group test keeps for a given person.
- Recommend a group-based rule or a data-driven USERNAME() comparison from how access is managed and how many groups it needs.

Key terms:
- **Group function:** ISMEMBEROF, which tests membership in a Tableau group.
- **User function:** a function that returns or tests the signed-in user's own identity, such as USERNAME().
- **Literal string:** a value typed in quotes in the calculation, not a field reference.
- **User filter:** a calculated field such as `[Username field] = USERNAME()` used as a filter so people see only their data.
- **Session:** a user's visit to a workbook or view; group changes apply from the next one.

## Key facts

| Fact | Detail | Source |
|---|---|---|
| ISMEMBEROF output | TRUE, FALSE, or NULL when not signed in | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| Membership source | Tableau groups on Tableau Cloud or Tableau Server | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| Arguments of ISMEMBEROF, ISUSERNAME, ISFULLNAME | Literal strings, not fields | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| Special characters | HTML URL encoding; _ ( ) ! permitted unencoded | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| "All Users" | ISMEMBEROF returns TRUE | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| Membership change | Seen in a new session; existing session is stale | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| USERNAME() in Desktop | Local or network username | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| True option for a user filter in Desktop | Visible only after signing in to Server or Cloud | [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm) |
| Dynamic user filter | Needs the security information in the data | [RLS options](https://help.tableau.com/current/server/en-us/rls_options_overview.htm) |

## Check yourself

- Why can a USERNAME() filter behave differently in Tableau Desktop than on the site?
- Which special characters can appear in a group name passed to ISMEMBEROF without HTML URL encoding?
- Why does appending OR ISMEMBEROF('All Users') to a filter open the data to everyone?
- What does ISFULLNAME("Hamlin Myrer") return for a signed-in user whose full name is different?

## Sources

- [User Functions](https://help.tableau.com/current/pro/desktop/en-us/functions_functions_user.htm)
- [Create a User Filter and Secure it for Publishing](https://help.tableau.com/current/pro/desktop/en-us/publish_userfilters_create.htm)
- [Overview of Row-Level Security Options in Tableau](https://help.tableau.com/current/server/en-us/rls_options_overview.htm)
- [RLS Best Practices for Data Sources and Workbooks](https://help.tableau.com/current/server/en-us/rls_bestpractices.htm)

## About the full unit

The "Core concepts", "Exam traps" and "Worked scenario" sections of this unit, its 8 linked practice questions, and unlimited timed mock exams are included with the Tableau Consultant pack (USD $19): https://www.certifyforce.com/practice-exams