Basic operation of MongoDB

The basic operations of MongoDB are: Add delete update and read

Start MongoDB Shell: Command line input MONGO (Centos 7)

[[email protected] test] # MONGO MongoDB Shell version:2.6.122017-08-31t17:54:18.621+0800 for are set to 4096KB 2017-08-31t17:54:18.621+0800 [Initandlisten] * *          or  less 2017-08-31t17:54:18.621+0800 [ Initandlisten] * *          http://dochub.mongodb.org/core/readahead

To add a document:

> Db.test.insert ({"key_a":"value_a"" ninserted " : 1 }" > Db.test.insert ({"key_b":"value_b "" ninserted": 1}) 

To read a document:

Find () can query multiple qualifying documents, FindOne () queries only one,

>Db.test.find () {"_id": ObjectId ("5a12da411c97109757a27d5d"),"key_a":"value_a" }{ "_id": ObjectId ("5a12dab51c97109757a27d5e"),"Key_b":"Value_b"}

>"_id" : ObjectId ("5a12da411c97109757a27d5d" " key_a " " value_a " }

> Db.test.findOne ({"Key_b":"Value_b"}){ "_id": ObjectId ("5a12dab51c97109757a27d5e"),"Key_b":"Value_b" }> Db.test.findOne ({"_id": ObjectId ("5a12da411c97109757a27d5d")}){ "_id": ObjectId ("5a12da411c97109757a27d5d"),"key_a":"value_a"}

To update a document:

> Db.test.insert ({"Key_c":"Value_c"}) Writeresult ({"ninserted": 1 })
> Db.test.findOne ({"Key_c":"Value_c"}){ "_id": ObjectId ("5A12E0A38710E2C2442EDA15"),"Key_c":"Value_c" }
> Db.test.update (Db.test.findOne ({"Key_c":"Value_c"}),  {"New_key_c":"New_value_c","Key_c":"Value_c"}) Writeresult ({"nmatched": 1,"nupserted": 0,"nmodified": 1 })
> Db.test.findOne ({"Key_c":"Value_c"}){    "_id": ObjectId ("5A12E0A38710E2C2442EDA15"),    "New_key_c":"New_value_c",    "Key_c":"Value_c"}

To delete a document:

> db.test.remove ({"key_c":"value_c"" nremoved " : 1 }" > Db.test.findOne ({"key_c":"value_ C"}) null

Basic operation of MongoDB