mongodb distinct去重

// 
> db.addresses.insert({"zip-code": 10010}) 
> db.addresses.insert({"zip-code": 10010}) 
> db.addresses.insert({"zip-code": 99701}) 
 
> // shell helper: 
> db.addresses.distinct("zip-code"); 
[ 10010, 99701 ] 
 
> // running as a command manually: 
> db.runCommand( { distinct: 'addresses', key: 'zip-code' } ) 
{ "values" : [ 10010, 99701 ], "ok" 
// 
> db.comments.save({"user": {"points": 25}}) 
> db.comments.save({"user": {"points": 31}}) 
> db.comments.save({"user": {"points": 25}}) 
 
> db.comments.distinct("user.points"); 
[ 25, 31 ]