1.db.eval()执行Javascript脚本
2.DBREF文档引用
> db.user.insert({"_id":"mike","display_name":"Mike D"})
> db.user.insert({"_id":"kristina","display_name":"Kristina C"})
> db.notes.insert({"_id":5,"author":"mike","text":"MongoDB is fun!"})
> db.notes.insert({"_id":20,"author":"kristina","text":"...and DBRefs are easy,t
oo","references":[{"$ref":"users","$id":"mike"},{"$ref":"notes","$id":5}]})
> var note=db.notes.findOne({"_id":20});
> note.references.forEach(function(ref){
... printjson(db[ref.$ref].findOne({"_id":ref.$id}));
... });
null
{ "_id" : 5, "author" : "mike", "text" : "MongoDB is fun!" }
>
{"$ref":集合名称,"$id":_ID,"$db":数据库名称}
可实现跨数据库，跨集合的引用。
3.db.system.js.insert()用来存储JavaScript