I have a unique index on the table and I need to make it case-insensitive, because I started getting duplicates in that table:

```
TEST
Test
TeSt

```

To fix the issue I was trying to drop existing index and re-create it:

```
 ALTER TABLE table1 drop constraint test_uk1;
 DROP INDEX test_uk1;
 CREATE UNIQUE INDEX test_uk1 ON table1(UPPER(column1));

 ALTER TABLE table1 ADD CONSTRAINT test_uk1 UNIQUE (column1) USING INDEX test_uk1 ENABLE VALIDATE;

```

I got an error `ORA-14196: Specified index cannot be used to enforce the constraint.` on the last statement.

Is there a better way to accomplish this with Oracle?