"Duplicate entry" error using utf8_unicode_ci

[Paul Deuter]

We have a UNIQUE varchar column with character set utf and collate utf8_unicode_ci.

We correctly get a duplicate entry error when we try to insert "ab" and then "Ab". But we also get a duplicate entry error when we try to insert "äb". For purposes of collation (i.e. sorting), it is clear that a should be treated as equal to ä. But for the purpose of inserting unique data into this column, a is not equal to ä. Am I wrong here?

Is there a collation that treats "ä" and "Ä" as equal and "a" and "A" as equal, but "a" not equal to "ä" and "A" not equal to "Ä"?

Thanks,
Paul