How can I do $and queries against an array in Mongo?

I have a collection in mongo where objects appear as follows:

{ name:"Scott", bio:"Stumped", roles:["USR","ADM"] }

Many more roles are possible. I want to perform any combination of intersection queries, like so:

db.coll.find({$and:[{roles:"USR"},{roles:{$ne:"ADM"}}]})

Some queries may be all role =, some may be all roles !=, and some may be mixed as with the above example. I have had some measure of success with $or and $nor, but absolutely no query I can fathom works with $and. I have even tried leveraging $where and $elemMatch to emulate what I want. I am also really trying to avoid multiple que开发者_运维知识库ries w/ the application handling intersection. Ideas?

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Found the answer:

db.coll.find( {roles : { $all : ["USR"], $nin : ["ADM"]}} )

Thanks Hohhi for leading me down the right path!

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db.coll.find("roles":{$all:["USR","ADM"]}})

I think this would help you, at least it returns the result you are looking for