Sorry, I'll remake (rewrite? redo? ... bad English :/ ) my question: I have Books, Authors and Intermediate table. At intermediate I'm currently using the following indexes: CREATE INDEX authorIndex ON Intermediate(author_id); CREATE INDEX bookIndex ON Intermediate(book_id); I need a third index to not allow duplicated data in my table: CREATE UNIQUE INDEX blablabla ON Intermediate(author_id, book_id); I'd like to know if, using the third index I can delete one of the first. Maybe both? Thank you! Bye! -- Silas Justiniano - Brazil