title: Unique combination of fields in SQLite?
body: <p>I'm trying to populate a new SQLite database with rows based on a set of data, but I'm having trouble with avoiding duplicate rows.  I could accomplish this in Python, but there certainly must be a design option in SQLite to handle this.</p>
  
  <p>I need each row to exist for only a unique combination of three text fields.  If I make each text field constrained with UNIQUE, then all three must be unique.  But I would instead like a unique combination of the three strings.  </p>
  
  <p>In other words, these records should all be able to exist:
  (a, a, a)
  (a, a, b)
  (a, b, b)
  (b, b, b)</p>
  
  <p>If I make all three fields UNIQUE and insert those rows, only (a,a,a) and (b,b,b) are inserted.  I could concatenate fields 1-3 in Python and use that as a primary key, but it seems like extra work. </p>