MongoDB Super Concise Introductory tutorial

1. Concept paper

MongoDB and MySQL are representatives of non-relational databases and relational databases, which can quickly build up the cognition of MongoDB through the contrast between them.

MongoDB	MySQL
Databases (database)	Databases (database)
Collection (Collection)	Tables (table)
Documents (document)	Records (record)

For relational databases, in general, we can simply understand that: a database management application, you can create multiple databases (databases), each database can manage many tables (tables), the table is stored in the curd can be recorded (records), This level of management can also be mapped to MongoDB.

Unlike MySQL, MongoDB's data has a flexible pattern. The collection itself does not have a regular check of the document structure, and the design of the table constrains the name of the containing field from the beginning.

It is important to note that MongoDB, as a non-relational database, does not mean that we cannot design a relational structure when we use it, and we can also artificially constrain the type of data contained in the document structure, (unlike MySQL, MongoDB's documentation supports arrays and objects, Sub-documents and other complex data structures can also be designed to resemble the ER diagram of the relationship model.
The following is an example of a book classification tree structure data modeling provided by the official website
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The design idea of the traditional relational database is to treat each node as a record, and each node holds the _id of its parent node.

_id	Parent
Mongodb	Databases
Dbm	Databases
Databases	Programming
Languages	Programming
Programming	Books
Books	Null

This relationship can also be used with MongoDB storage

db.categories.insert( { _id: "MongoDB", parent: "Databases" } )db.categories.insert( { _id: "dbm", parent: "Databases" } )db.categories.insert( { _id: "Databases", parent: "Programming" } )db.categories.insert( { _id: "Languages", parent: "Programming" } )db.categories.insert( { _id: "Programming", parent: "Books" } )db.categories.insert( { _id: "Books", parent: null } )

For several other tree-shaped structures, please refer to the modeling methods
Model Tree Structures
Modeling a Tree in a Document Database

2. Quick-Action article

• Download Install client https://docs.mongodb.com/manual/administration/install-community/

• Open MongoDB Service
  (1) Create a database storage directory

  mkdir -p ~/yourdir/db

  Ensure that the current user has read and write access to the directory
  (2) Open service

  mongod --dbpath <path to data directory>

  Before this, make sure that the Mongod command path has been added to the system environment variable

• Using the MONGO shell to manipulate the database
  (1) Connect to the database and open command mode

  mongo --host 127.0.0.1:27017

  If you use the default parameters, the following arguments can be omitted
  (2) A database showing the current operation

  db

  (3) Switch database

  use <database>

  MongoDB automatically creates databases and collections when data is stored for the first time in a database

  use myNewDatabasedb.myCollection.insertOne( { x: 1 } );

  The above insertOne statement automatically creates the myNewDatabase database, with the myCollection collection.

3.MongoDB additions and deletions to check operation

• Increase

• By deleting

db.collection.deleteOne()db.collection.deleteMany()

• Change

db.collection.updateOne()db.collection.updateMany()db.collection.replaceOne()

• Check

db.collection.find()

MongoDB Super Concise Introductory tutorial