title: Difference between MongoDb Index and SQL Index
body: <p>Is there a difference between two index concepts? MongoDB is a type of "NoSQL" implementation and its data can be scattered among nodes. Does this feature make index concept differ from that of relational DB? </p>
  
  <p>I mean, in a relational DB, an index is applied on each column and one corresponding index table is created.</p>
  
  <p>With a NoSQL DB index, does each node has its own index table for each collection it stores?</p>