比如说我需要在 MongoDB 中存储公司的各部门信息，结构大概是这样的：

公司
    部门A
        部门A属性1
        部门A属性2
        部门A员工
            员工A1及其信息
            员工A2及其信息
            员工A3及其信息
            员工A4及其信息
    部门B
        部门B属性1
        部门B员工
            员工B1及其信息
            员工B2及其信息
            员工B3及其信息

请问在 MongoDB 中应该如何存储这个结构？

> db.department.find()
{ "_id" : ObjectId( "1" ), "attrA1" : "", "attrA2" : "", "staff" : [ { "name" : "A1" } , { "name" : "A2" } ] }
{ "_id" : ObjectId( "2" ), "attrB1" : "", "attrB2" : "", "staff" : [ { "name" : "B1" } , { "name" : "B2" } ] }

还是：

> db.department.find()
{ "_id" : ObjectId( "1" ), "attrA1" : "", "attrA2" : "" }
{ "_id" : ObjectId( "2" ), "attrB1" : "", "attrB2" : "" }
>db.department.staff.find()
{ "_id" : ObjectId("3"),  "name" : "A1", "department": [ { "$ref" : "department", "$id" :  ObjectId( "1" ) } ] }
{ "_id" : ObjectId("4"),  "name" : "A2", "department": [ { "$ref" : "department", "$id" :  ObjectId( "1" ) } ] }
{ "_id" : ObjectId("5"),  "name" : "B1", "department": [ { "$ref" : "department", "$id" :  ObjectId( "1" ) } ] }
{ "_id" : ObjectId("6"),  "name" : "B2", "department": [ { "$ref" : "department", "$id" :  ObjectId( "1" ) } ] }

或者应该怎么组织这个结构才好？