This is the documentation page for a particular constraint type. SeeHelp:Property constraints portal for a general overview of property constraints.

distinct-values constraint(Q21502410) specifies that values for this property should be unique across all of Wikidata, and no other entity should have the same value in a statement for this property.

Almost all (external) identifier properties have such a constraint, since anISBN-13(P212) orFreebase ID(P646) should uniquely identify an entity. Other examples includeflag(P163) andanthem(P85). AlsoCommons category(P373) should be unique because those categories typically have a unique Commons sitelink.

Properties with this constraint usually also havesingle-value constraint(Q19474404).

If noconstraint scope(P4680) is specified, this constraint is only checked on the main value of a statement.

A qualifier can be defined asseparator(P4155). This allows the same value on multiple entities as long as the separator qualifier is different.

There are several possible ways to address a violation of this constraint:

• It’s possible that the conflicting items are duplicates and should be merged.
• It’s possible that the property value is erroneous on one of the conflicting items (e. g. a typo, accidentally transposed digits, etc.) and should be fixed.
• It is possible that aseparator(P4155) (or several of them) should be defined for the constraint, to declare that multiple items sharing a value are acceptable as long as they have certain different qualifiers.
• It’s possible that the conflicting items are a rare, but legitimate exception to the constraint, and nothing should be done.

This constraint has one optional parameter:

separator(P4155)

Contains the separators. May contain one or more properties. If specified, multiple statements with the same value do not constitute a violation of this constraint as long as they have different qualifiers for the properties specified here.

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When the constraint is set to the property, the following template is automatically displayed in the property talk page. The template is created byModule:Constraints usingTemplate:Constraint, invoked fromTemplate:Property documentation. Translations are defined atModule:i18n/constraints.

Distinct values: this property likely contains a value that is different from all other items. (Help)

Exceptions are possible as rare values may exist.Exceptions can be specified usingexception to constraint(P2303).
List of violations of this constraint:Database reports/Constraint violations/P236#Unique value,SPARQL (every item),SPARQL (by value)

Cases where uniqueness should or could be evaluated differently and ways to handle such exceptions:

• list exceptions as such on property constraints: available^[1]
• indicate that an identifier is shared with another item: not available^[2]
• indicate that an identifier was reassigned: not available
• distinct best value constraint: not available^[3]
• distinct case insensitive: not available, handling attempted by normalizing values^[4]
• distinct value including uses in references: available^[5]
• define uniqueness per namespace: not available^[6]
• define uniqueness per entity type (e.g. lexeme and item): not available

Lists of properties which are set distinct values constraint.

• Category:Properties with single value constraints
• SPARQL query - click the execute button at the linked page to see the query result.

• Help:Properties
• Help-en
• Properties with unique value constraints