How to: Delete Unique Constraints
Delete a unique constraint when you want to remove the requirement for uniqueness for values entered in the column or combination of columns included in the constraint expression.
Note
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To delete a unique constraint
In Server Explorer, select the table with the unique constraint, and from the Database menu click Open Table Definition.
The table opens in Table Designer.
From the Table Designer menu, click Indexes/Keys.
In the Indexes/Keys dialog box, select the unique key in the Selected Primary/Unique Key and Index list.
Click Delete.
The constraint is removed from the database when you save the table.