Many times on a survey the answer to a question needs to be unique. For example a class code, a student ID, a patient NHS number, and so on.

In Epicollect5 there are two distinct types of uniqueness:

  • Form: uniqueness is across all the entries of a form

  • Hierarchy: uniqueness is across all the child entries of a form (the parent entry is considered)

If your project has got a single form only, the uniqueness is always set to form. This means if you set a question like "What is your name" as unique, you cannot have the same name more than once.

The comparison is case insensitive i.e. "John" and "john" are the same, despite the capital letter of "John".

If you have multiple forms, for each child form you have the option to decide if you want the answer to the question unique form wide or hierarchy wide. On a project featuring UNIVERSITY as the parent form, and DEPARTMENT as the child form, let's imagine you enter "Imperial College" as a UNIVERSITY entry and then you add DEPARTMENT entries to it, like Biology, History, Media etc.

If you would like to avoid having the same department entered more than once for a single UNIVERSITY entry, you might set the uniqueness on the DEPARTMENT name. If you set DEPARTMENT name to be unique as form though, you could enter "Biology" only once, regardless of the UNIVERSITY being Imperial College or another one, like Stanford. This would not work as "Biology" is a common department across universities in the world.

Form uniqueness:

The solution is to set the uniqueness as hierarchy, to have the parent entry considered. This way the "Biology" DEPARTMENT can be entered only once but for each UNIVERSITY entry.

Hierarchy uniqueness:

To set the uniqueness for a question, select the question and go to the "Advanced" tab:

The first option is the form uniqueness, and the second option is the hierarchy uniqueness as described.

The form(s) names will differ based on your project form names.

The uniqueness constraint is available for the following question types:

  • TEXT



  • DATE

  • TIME



Date & Time uniqueness

The uniqueness of DATE and TIME questions is based on the format selected.

DATE answers are saved in ISO 8601 format, without timezone and with the time set to midnight, i.e `2022-01-15T00:00:00.000` therefore the comparison is done only on the date part.

TIME answers are saved in ISO 8601 format i.e 2022-05-12T12:34:45.000but the date part is not considered for the uniqueness.

Last updated