小编tro*_*ope的帖子

> db.test.insert({"a" : { "b" : { "c" : { "d1" : [ "e1" ],
                                          "d2" : [ "e2" ], 
                                          "d3" : [ "e3", "e4" ], 
                                          "d4" : [ "e5", "e6" ] } } } })
> db.test.find({'a.b.c' : {$exists : true}})
{ "_id" : ObjectId("4daf2ccd697ebaacb10976ec"), "a" : { "b" : { "c" : { "d1" : [ "e1" ], "d2" : [ "e2" ], "d3" : [ "e3", "e4" ], "d4" : [ "e5", "e6" ] } } } …