title: Is there any sql database not creating an index for a unique constraint?
body: <p>I have seen <a href="https://stackoverflow.com/questions/9764120/does-a-unique-constraint-automatically-create-an-index-on-the-fields">this question</a>, but really, it's only about MySQL. <strong>Is there any sql database out there, that does not create an index for a unique constraint?</strong></p>