SharePoint 2010 Enforce Unique Column Values

In SharePoint 2010 it is possible to enforce unique values for a column. To enforce unique values, the column has to be indexed. Only columns that can be indexed can enforce unique value constraint.

The columns that can enforce unique values include:

• Single line of text (not case sensitive; for e.g “Lazy Brown FOX” and “lazy brown Fox” will be treated as duplicates)

• Choice field (only Drop-Down menu and Radio Button)

• Number

• Currency

• Date and Time

• Lookup

How to enable Enforce unique values

• Click Create Column from List Tools > List tab
• Select Yes radio button for Enforce unique values

If the column has not been indexed, a message appears stating that the column has to be indexed.

Modify list column to enforce uniqueness

If the column of an existing list is modified to enforce unique values, an error message pops-up if there are duplicates in the list. You are required to remove the duplicates before enforcing uniqueness

SharePoint 2007

SharePoint 2007 does not have the feature to enforce unique column constraint. However, there are several solutions to enforce unique values; using  jQuery is one of them. Refer to this article that explains how it is done.

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