Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.

I used query with left outer joins.

First i used Server Explorer to drag and drop my table, than i modified query.

When i draged and droped my table there was unique field (id) with key logo. Because of joins, query returned more than one unique id, so solution is:

Make this unique field (id) property "Unique" into False.

That solved my problem.