Another little doubt: I've already asked that in #postgresql at freenode, but I didn't understand well. I have two tables: Books - book_id - name Authors - author_id - name One book can have many authors and one author can have many books. To make that possible, I need a third table: Intermediate - book_id - author_id My question is about the indexes in Intermediate table. Is the following index: CREATE UNIQUE INDEX foo ON Intermediate(book_id, author_id); enough for every query I want to perform? Or should I need CREATE UNIQUE INDEX foo ON Intermediate(book_id, author_id); CREATE UNIQUE INDEX bar ON Intermediate(book_id); CREATE UNIQUE INDEX baz ON Intermediate(author_id); too? Thank you very much. Bye!
