MongoDB (i) MongoDB introduction

MongoDB is a cross-platform, document-oriented database that provides high performance, high availability, and scalability convenience. MongoDB works on the concept of collection and documentation.

Database

A database is a collection of physical containers. Each database has its own set of files on the file system. A single MongoDB server typically has multiple databases.

Collection

A collection is a set of MongoDB documents. It is equivalent to an RDBMS table. The collection exists in a single database. The collection does not execute the pattern. The documents within the collection can have different areas. Typically, all files in a collection are of the same or related purpose.

Document

A document is a set of key-value pairs. File dynamic mode. Dynamic mode refers to documents in the same collection that do not require a collection of common fields that have the same field or structure group, and can accommodate different types of data.

The table given below shows RDBMS terminology using MongoDB relationships

RDBMS	MongoDB
Database	Database
Table	Collection
Tuple/row	Document
Column	Field
Table Join	Embedded Documents
Primary Key	Primary Key (Default key _id provided by MongoDB itself)
Database Server and Client
Mysqld/oracle	Mongod
Mysql/sqlplus	Mongo

Sample Document

The example given below shows a blog site, which is simply a comma-separated key-value pair for the document structure.

{_id:objectid (7df78ad8902c) title:' MongoDB Overview ', Description:' MongoDB is no SQL database ', by:' Tutorials Point ', URL:' Http://www.yiibai.com ', Tags: [' MongoDB ', ' database ', ' NoSQL '], likes:100, Comments: [{User:' User1 ', message:' My first comment ', dateCreated:NewDate (2011,1,20,2,15), like:0}, {User:' User2 ', message:' My second Comments ', dateCreated:NewDate (2011,1,25,7,45), like:5      }   ]}

_ID is a 12-byte hexadecimal number that guarantees the uniqueness of each document. You can provide _id to insert the document at the same time. If not provided, then each document of MongoDB provides a unique ID. These 12 bytes, the first 4 bytes are the current timestamp, the next 3 bytes of the machine ID, the next 2 bytes of the process ID of the MONGODB server and the remaining 3 bytes are simple increment values.

MongoDB (i) MongoDB introduction