MongoDB (1) Introduction

I. A brief introduction of NoSQL

The structured programming provided by RDBMS (relational database) makes data modeling and application programming very simple, with very high economic benefits, and low learning costs. However, in today's data explosion era, every moment will be a huge amount of data generation, the data read and write requirements are more and more high, RDBMS can not meet the needs of people, NoSQL was born.

NoSQL (not only SQL) means: No longer just a structured query, it is completely different from the RDBMS's data storage structure, only to ensure that the final consistency of the data rather than adhere to the acid principle, read and write performance far more than the RDBMS database. is essential in big data storage.

Common NoSQL such as:

1) Redis

2) MongoDB

3) memcached

Ii. introduction of MONGO

MONGO is also a nosql, but unlike Redis, it's somewhere between NoSQL and RDBMS. Written in C + +, is a distributed file storage of open-source database system, with high performance, high availability, easy to expand and other features. The basic data structure is: key-value structure, can analogy JSON data structure to understand MONGO data structure.

Let's take a look at four key concepts:

1) Data Base (database)

As with all database systems, MONGO can also create multiple independent database,database to store data.

2) Set (collection)

We can understand collection,collection stored in database by analogy to the concept of "table" of RDBMS.

3) Documentation (document)

We can understand document,document exists in collection by analogy to the concept of "line" in RDBMS.

4) Domain (field)

We can understand that Field,field exists in document by analogy to the concept of "column" of the RDBMS.

Such as:

Third, the data type

Td>string

data type	description
string
integer	integer
Boolean	Boolean
double	double precision
min/max keys	set a value and the lowest value of Bson and Highest value comparison
array	array or list
Timestamp	timestamp
Object	for inline documents
Null	create null value
symp OL	symbol, usually identical to string
date	date time
Object ID	Object ID
binary Data	binary
Code	JS script code
Regular expression	Regular Expressions

The above data types specifically mention the object ID, which is similar to a unique primary key that can be quickly generated and sorted, including 12byte:

0-3 bytes is time stamp of GMT (8 hours late in Beijing)

4-6 is the machine identification code

7-8 is the process ID

9-11 is a random number.

The document stored in the MONGO must have a _id key. The value of this key can be any type, but the default is the object ID.

Since Objectid saves the timestamp of the creation by default , you do not need to save the timestamp field for your document, and you can get the timestamp by Gettimestamp. Such as:

var newObject = ObjectId ()> newobject.gettimestamp () isodate ("2017-11-25t07:21:10z")

Iv. Summary

MONGO in C + +, is a distributed file storage open source database, high performance, high availability, easy to expand, the data structure is similar to the structure of JSON, support rich data types.

MongoDB (1) Introduction