In the target table add a serial datatype column as part of the unique constraint.
Do not populate this column explicitly on insert, but have the db do it for you. It will allocate an incremental (unique) value automatically on insert.
But I think your problem is more fundamental - if you genuinely have duplicate values in a column - there should not be a unique constraint on it. If it should be unique, then you should modify your insert data.
I Can't modify my insert data, because there's a PHP RANDOM CODE that does exactly what I wanna do with the SQL - It generates a random but unique value for the column "code" - So the customer will be able to have duplicates values on that column
Today the PHP is already generating for example:
code_321525694417ad6b5f
So that is linked to another table (I can do that manually no problem)
