title: Indexing individual fields of SQL Server composite keys
body: <p>I'm upsizing a Jet database to SQL Server Express 2008 R2 and before doing so, I'm re-evaluating the schema (it was designed in 1997-98, and the guy who designed it (i.e., me) was something of a moron!). </p>
  
  <p>My question is about N:N join tables with a two-column composite key. In Jet, joins on the first column of a two-column composite key will use the composite index, but joins on the second column will not, so in general, in Jet databases with large N:N join tables with reasonably large numbers of records, in addition to the composite index I add a second, non-unique index on the second column.</p>
  
  <p>Is this a good idea in SQL Server?</p>
  
  <p>(Maybe it's not a good idea in Jet?)</p>