//常规查询

db.getCollection('test').find({}).sort({_id:-1}).limit(2)

 

//模糊查询

db.getCollection('test').find({"b":{$regex:''}})


db.getCollection('test').find({"$where":"this.detail&&this.detail.indexOf('table)>-1"})

 

数组元素查询

db.getCollection('test').find({"list.a":668})

 

聚合查询

db.getCollection('test').aggregate([
{ "$match" : { "StudentId" : "e3379646-7023-4fa4-a98f-e7ad683e0f32", "TotalNumbers" : { "$gt" : 0 } } },
{ "$group" : { "_id" : "$ApplicationId" , "CorrectRate" : { "$avg" : { "$divide" : ["$CorrectNumbers", "$TotalNumbers"] } } } },
{ "$match" : { "CorrectRate" : { "$lt" : 1 } } },
{ "$sort" : { "CorrectRate" : 1 } },
{ "$project" : { "_id" : 0, "ActivityId" : "$_id", "CorrectRate" : "$CorrectRate" } },
{ "$limit" : 20 }])

 

//更新单个字段
db.test.update({a:0},{$set:{'b':0}},{multi:true})

 

//删除单个字段

db.test.update({a:0},{$unset:{'b':0}},{multi:true})

 

// 覆盖更新
db.test.update({a:1},{b:2})

 

//更新子元素数组
db.test.update({"list.a":668},{$set: {'list.$.b':"666"}},{multi:true})

 

//追加子元素
db.test.update({"list.a":668},{$push: {'list':{ 'a': 665,'er':"1234" }}},{multi:true})


// 删除子元素数组
db.test.update({},{$pull: {'list':{ 'a': 665 }}},{multi:true})

 

实现group by 多个key having count(*) >1

db.test.aggregate(

{"$group": {_id:{card:"$card",account:"$account"}, "count": { "$sum": 1 } } },

{"$match": {"_id" :{ "$ne" : null } , "count" : {"$gt": 1} } }

)