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Asked: 2026-05-17T20:04:44+00:00

I have a table, something like FieldsOnForms( FieldID int (FK_Fields) FormID int (FK_Forms) isDeleted

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I have a table, something like 

FieldsOnForms(
 FieldID int (FK_Fields)
 FormID int (FK_Forms)
 isDeleted bit
)

The pair (FieldID,FormID) should be unique, BUT only if the row is not deleted (isDeleted=0).

Is it possible to define such a constraint in SQLServer 2008? (without using triggers)

P.S. Setting (FieldID, FormID, isDeleted) to be unique adds the possibility to mark one row as deleted, but i would like to have the chance to set n rows (per FieldID,FormID) to isDeleted = 1, and to have only one with isDeleted = 0

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1 Answer

  1. Editorial Team

    You can have a unique index, using the SQL Server 2008 filtered indexes feature, or you can apply a UNIQUE index against a view (poor man’s filtered index, works against earlier versions), but you cannot have a UNIQUE constraint such as you’ve described.

    An example of the filtered index:

     CREATE UNIQUE NONCLUSTERED INDEX IX_FieldsOnForms_NonDeletedUnique ON FieldsOnForms (FieldID,FormID) WHERE isDeleted=0
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