未知的运算符:$和MongoDB中

我正在通过node.js代码查询mongodb。 我的mongo文档集(患者集合)具有以下结构:+

Patient collection { "_id" : ObjectId("59e5c28f37ce021e142e7ead"), "MRN" : "00126389", "Family_Name" : "Jones", "First_Name" : "Lydia", "Father_Name" : "Bob", "Maiden_Name" : "", "Mother_Name" : "n/a", "Spouse_Name" : "", "Address" : "", "Telephone_Nbr" : "", "Patient_Visit" : { "Department" : "ER", "Hospital_Status" : "Active", "Case_Nbr" : "17", "Admission_Date" : "01/04/2011 12:00:00 AM", "Admission_Time" : "14:02" } } 

我的查询执行代码如下所示:

 mongoClient.connect(mongoConstr, function(err, db) { if (err) throw err; var query = { $and: [{ "Patient_Visit.Department": "ER" }, { $or: [{ "Patient_Visit.Hospital_Status": "Active Left" }, { "Patient_Visit.Hospital_Status": "Active" }] }] }; var cursor = db.collection("tbl_Patients").find({ query }); cursor.forEach(function(doc) { console.log(JSON.stringify(doc)); }, function(err) { db.close(); throw (err); }); }); 

当请求被执行时,我得到以下错误:

 MongoError: unknown operator: $and 

任何帮助,将不胜感激。

用查询replace{query}。

 var cursor = db.collection("tbl_Patients").find(query);