How to create a unique field of type TEXT?

Question

MySQL

There are no problems with the varchar type. Set a unique value. But what if you need to store a unique value of type TEXT

Answer 1

Hang up an additional field of type varchar, set it unique and create a trigger that works on insert / update which calculates md5 for the text field and writes it to the varchar field. The trigger executes before writing or updating. If the md5 matched, then the text matched, and this will throw an exception.
Sobsno that's the whole focus.

Answer 2

no way. and why is that at all?

Answer 3

Do you want that there are no two identical texts in the database? Then:
$text = md5($text);