mongodb

CRUD operations on Array objects nested within an Object in MongoDB Spring Boot

由 前提是你 提交于 2021-02-17 05:37:29
问题 I have a MongoDB object which was created using a Map<String, List>. I'm trying to add CRUD methods to EDIT and DELETE objects from the arrays within the object. This is how the JSON structure looks like: [ { "id": "1", "courses": { "Spring": [ { "subject": "Electrical Engineering", . . . "id": "123" } ], "Fall": [ { "subject": "Electrical Engineering", . . . "id": "456" }, { "subject": "Computer Science", . . . "id": "789" } ] } } ] I was trying to use pull() method to remove the object but

CRUD operations on Array objects nested within an Object in MongoDB Spring Boot

由 [亡魂溺海] 提交于 2021-02-17 05:37:25
问题 I have a MongoDB object which was created using a Map<String, List>. I'm trying to add CRUD methods to EDIT and DELETE objects from the arrays within the object. This is how the JSON structure looks like: [ { "id": "1", "courses": { "Spring": [ { "subject": "Electrical Engineering", . . . "id": "123" } ], "Fall": [ { "subject": "Electrical Engineering", . . . "id": "456" }, { "subject": "Computer Science", . . . "id": "789" } ] } } ] I was trying to use pull() method to remove the object but

Mongoimport ignore leading zero in csv

由 假装没事ソ 提交于 2021-02-17 05:13:20
问题 I have a .CSV export file from a SQL Server database, with a phone number field (number type) that field values started with leading zero. Leading zero is presented in the CSV file. When I attempt to mongoimport it to DB (in string type) I find data imported without leading zero. The target field number is string. How can I solve this problem? 回答1: you can specifically define the type of the field using the import option --columnsHaveTypes Instructs mongoimport that the field list specified

Mongoimport ignore leading zero in csv

由 我们两清 提交于 2021-02-17 05:13:19
问题 I have a .CSV export file from a SQL Server database, with a phone number field (number type) that field values started with leading zero. Leading zero is presented in the CSV file. When I attempt to mongoimport it to DB (in string type) I find data imported without leading zero. The target field number is string. How can I solve this problem? 回答1: you can specifically define the type of the field using the import option --columnsHaveTypes Instructs mongoimport that the field list specified

MongoDB: How to query a time-series with incomplete data?

由 时光总嘲笑我的痴心妄想 提交于 2021-02-17 04:40:28
问题 I'm storing time series data in a mongoDB collection with one data point every 15min. But sometimes, due to bad conditions, some data points get lost. I have a dataset as follows: {"device_id": "ABC","temp": 12,"timestamp": 2020-01-04T17:48:09.000+00:00} {"device_id": "ABC","temp": 10,"timestamp": 2020-01-04T18:03:09.000+00:00} {"device_id": "ABC","temp": 14,"timestamp": 2020-01-04T18:18:09.000+00:00} missing frame missing frame {"device_id": "ABC","temp": 13,"timestamp": 2020-01-04T19:03:09

总结：被MySQL UTF8编码坑的惨痛教训...

由 旧城冷巷雨未停 提交于 2021-02-17 04:30:30
最近遇到几个项目被MySQL的utf8编码坑，想起之前编码问题被坑的惨痛教训，记录一下，警示自己。 曾几何时，每次建库都选utf8，觉得自己比那些用乱七八糟编码的人不知道酷到哪里去了。直到好多年前的某次课程设计做项目的时候，愉快的建了个用户表： CREATE TABLE `test_user` ( `id` int ( 11 ) unsigned NOT NULL AUTO_INCREMENT, `name` varchar ( 32 ) DEFAULT NULL , PRIMARY KEY ( `id` ) ) ENGINE = InnoDB DEFAULT CHARSET =utf8; 然后愉快的新增用户：INSERT INTO test_user(name) VALUES("我是😁")，接着愉快的反思人生： Incorrect string value : '\xF0\x9F\x98\x81' for column 'name' at row 1 我是谁？我来自哪里？我在干嘛？难道是我代码里面的字符集用错了？不对啊我所有地方都用的utf8啊…… # MySQL 的UTF8编码是什么？ 首先来看官方文档： The character set named utf8 uses a maximum of three bytes per character and contains

How to directly query nested field without specify parent field?

由 拥有回忆 提交于 2021-02-17 03:17:42
问题 I have next 3 documents in mongodb: document 1: { "name": "device1", "camera": { "number": 3 } } document 2: { "name": "device2", "camera": { "number": 1 } } document 3: { "name": "device3", "wifi": { "number": 2 } } My aim is to find all devices which modules' number > 1, the module maybe camera , wifi or others. I know I can use next to get the device: > db.devices.find({"camera.number":{$gt:1}}) { "_id" : ObjectId("5f436a3df716cb47d319245e"), "name" : "device1", "camera" : { "number" : 3 }

MongoDB 学习

由 和自甴很熟 提交于 2021-02-17 02:22:31
阅读目录 一 简介 二 MongoDB基础知识 三 安装 四 基本数据类型 五 CRUD操作 六 可视化工具 七 pymongo 一 简介 MongoDB是一款强大、灵活、且易于扩展的通用型数据库 1、易用性 MongoDB是一个面向文档（document- oriented）的数据库，而不是关系型数据库。 不采用关系型主要是为了获得更好得扩展性。当然还有一些其他好处，与关系数据库相比，面向文档的数据库不再有“行“（row）的概念取而代之的是更为灵活的“文档”（document）模型。 通过在文档中嵌入文档和数组，面向文档的方法能够仅使用一条记录来表现复杂的层级关系，这与现代的面向对象语言的开发者对数据的看法一致。 另外，不再有预定义模式（predefined schema）：文档的键（key）和值（value）不再是固定的类型和大小。由于没有固定的模式，根据需要添加或删除字段变得更容易了。通常由于开发者能够进行快速迭代，所以开发进程得以加快。而且，实验更容易进行。开发者能尝试大量的数据模型，从中选一个最好的。 2、易扩展性 应用程序数据集的大小正在以不可思议的速度增长。随着可用带宽的增长和存储器价格的下降，即使是一个小规模的应用程序，需要存储的数据量也可能大的惊人，甚至超出 了很多数据库的处理能力。过去非常罕见的T级数据，现在已经是司空见惯了。 由于需要存储的数据量不断增长

Mongodb findOne () not return value nodejs

由 柔情痞子 提交于 2021-02-17 02:07:15
问题 Hi Guys i try to do some email verification after a user suscrib to my api but when i do user.FindOne(token), the user is find but i not able to get the value of the user in the database the return me a big ass array and i don't see wich value to choose. my code: ValidationFunction: const User = require('../models/User'); const Token = require('../models/Token'); module.exports = function (req, res, next) { const headToken = req.header('token'); const token = Token.findOne({ token: headToken

Mongodb findOne () not return value nodejs

由 拜拜、爱过 提交于 2021-02-17 02:06:17
问题 Hi Guys i try to do some email verification after a user suscrib to my api but when i do user.FindOne(token), the user is find but i not able to get the value of the user in the database the return me a big ass array and i don't see wich value to choose. my code: ValidationFunction: const User = require('../models/User'); const Token = require('../models/Token'); module.exports = function (req, res, next) { const headToken = req.header('token'); const token = Token.findOne({ token: headToken
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