>use test > db.test.insert({"name":1})

>show dbs

> use test > db.dropDatabase()

> db.title.insert({"name":"hyx"})

> show collections

>use test >db.title.drop()

> db.file.insert({name:"huangyuxin",age:11})

>db.files.find()

> document=({by:"hyx"}){ "by" : "hyx" }> db.file.insert(document)WriteResult({ "nInserted" : 1 })> db.file.find(){ "_id" : ObjectId("5c6e8a060fc535200b893f29"), "name" : "huangyuxin", "age" : 11 }{ "_id" : ObjectId("5c6e8b1c0fc535200b893f2a"), "by" : "hyx" }>

> var res = db.file.insertMany([{"b": 3}, {'c': 4}])> res{    "acknowledged" : true,    "insertedIds" : [        ObjectId("5c6e8bba0fc535200b893f2b"),        ObjectId("5c6e8bba0fc535200b893f2c")    ]}> db.file.find(){ "_id" : ObjectId("5c6e8a060fc535200b893f29"), "name" : "huangyuxin", "age" : 11 }{ "_id" : ObjectId("5c6e8b1c0fc535200b893f2a"), "by" : "hyx" }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2b"), "b" : 3 }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2c"), "c" : 4 }>

> db.file.update({"name":"huangyuxin"},{$set:{"name":"hyx"}})WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })> db.file.find(){ "_id" : ObjectId("5c6e8a060fc535200b893f29"), "name" : "hyx", "age" : 11 }{ "_id" : ObjectId("5c6e8b1c0fc535200b893f2a"), "by" : "hyx" }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2b"), "b" : 3 }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2c"), "c" : 4 }{ "_id" : ObjectId("5c6e8cdf0fc535200b893f2d"), "name" : "hyx" }>

> db.file.save({"_id" : ObjectId("5c6e8b1c0fc535200b893f2a"),"name":"hyx"})WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })> db.file.find(){ "_id" : ObjectId("5c6e8a060fc535200b893f29"), "name" : "hyx", "age" : 11 }{ "_id" : ObjectId("5c6e8b1c0fc535200b893f2a"), "name" : "hyx" }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2b"), "b" : 3 }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2c"), "c" : 4 }{ "_id" : ObjectId("5c6e8cdf0fc535200b893f2d"), "name" : "hyx" }>

> db.title.find(){ "_id" : ObjectId("5c6e89060fc535200b893f27"), "name" : "yx" }> db.file.find(){ "_id" : ObjectId("5c6e8a060fc535200b893f29"), "name" : "hyx", "age" : 11 }{ "_id" : ObjectId("5c6e8b1c0fc535200b893f2a"), "name" : "hyx" }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2b"), "b" : 3 }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2c"), "c" : 4 }{ "_id" : ObjectId("5c6e8cdf0fc535200b893f2d"), "name" : "hyx" }> db.file.remove({"b":3})WriteResult({ "nRemoved" : 1 })> db.file.find(){ "_id" : ObjectId("5c6e8a060fc535200b893f29"), "name" : "hyx", "age" : 11 }{ "_id" : ObjectId("5c6e8b1c0fc535200b893f2a"), "name" : "hyx" }{ "_id" : ObjectId("5c6e8bba0fc535200b893f2c"), "c" : 4 }{ "_id" : ObjectId("5c6e8cdf0fc535200b893f2d"), "name" : "hyx" }>

>db.file.deleteMany({})

>db.file.deleteMany({ status : 1 })

> db.title.find({age:{$gt : 0}}){ "_id" : ObjectId("5c6f7d633ea8783bbfb7fd5e"), "age" : 10 }>

> db.title.find({age:{$gte : 1}})

> db.title.find({age:{$lt:13,$gt:10}}){ "_id" : ObjectId("5c6f7ded3ea8783bbfb7fd5f"), "age" : 12 }{ "_id" : ObjectId("5c6f7e833ea8783bbfb7fd60"), "age" : 12 }>

> db.title.find({"name" : {$type : 2}}){ "_id" : ObjectId("5c6e89060fc535200b893f27"), "name" : "yx" }>

> db.title.find().limit(2){ "_id" : ObjectId("5c6e89060fc535200b893f27"), "name" : "yx" }{ "_id" : ObjectId("5c6f7d633ea8783bbfb7fd5e"), "age" : 10 }>

> db.title.find({},{"name":1,_id:0}).limit(1){ "name" : "yx" }>

> db.title.find({},{'age':1,_id:0}).sort({age:1}){ }{ "age" : 10 }{ "age" : 12 }{ "age" : 12 }> db.title.find({},{'age':1,_id:0}).sort({age:-1}){ "age" : 12 }{ "age" : 12 }{ "age" : 10 }{ }>

>db.title.createIndex({"age":1})

>db.title.createIndex({"name":1,"age":-1})

>db.col.getIndexes()

>db.col.totalIndexSize()

>db.col.dropIndexes()

>> db.title.dropIndex({'age':1}){ "nIndexesWas" : 2, "ok" : 1 }>