title: Making combinations of attributes unique in PostgreSQL
body: <p>There is an option in postgresql where we can have a constraint such that we can have multiple attributes of a table together as unique</p>
  <pre><code>UNIQUE (A, B, C)
  </code></pre>
  <p>Is it possible to take attributes from multiple tables and make their entire combination as unique in some way</p>
  <p>Edit:</p>
  <p>Table 1: List of Book
  Attributes: ID, Title, Year, Publisher</p>
  <p>Table 2: List of Author
  Attributes: Name, ID</p>
  <p>Table 3: Written By: Relation between Book and Author
  Attributes: Book_ID, Author_ID</p>
  <p>Now I have situation where I don't want (Title, Year, Publisher, Authors) get repeated in my entire database</p>