二、MongoDB之CURD

try {
  db.accounts.insertOne( { "_id":1,user: "card", age: 15 } );
} catch (e) {
  print (e);
};

WriteError({
    "index" : 0,
    "code" : 11000,
    "errmsg" : "E11000 duplicate key error collection: users.accounts index: _id_ dup key: { _id: 1.0 }",
    "op" : {
        "_id" : 1,
        "user" : "card",
        "age" : 15
    }
})

查询操作

db.accounts.find()//查询所有文档
db.accounts.find().pretty()//结构化展示
筛选文档匹配查询
读取 user=yu的文档