Basic knowledge sorting of mongodb database

One 、NoSQL

understand Mongodb Let's get to know NoSQL,NoSQL yes Not Only SQL Abbreviation . Provided by lack SQL The storage and retrieval technology of the strictly restricted model of relational database . Mainly to simplify the design 、 Horizontal expansion and finer control of data availability .NoSQL There are many technologies, such as :Redis Key value structure of 、HBase Column structure of .

Two 、Mongodb

Mongodb It's also NoSQL A kind of . It is based on a document model that stores data objects as separate documents in a collection . Use it to provide high performance 、 High availability and automatically expanded data storage .

3、 ... and 、 aggregate

Mongodb Group data together by using sets . A collection is simply a set of documents with the same or similar purpose . Collections are similar to tradition SQL Table of database . It's just that collections don't enforce strict patterns , Documents in the same collection can have slightly different structures from each other .

Four 、 file

The document is Mongodb The representation of a single data entity in a database .SQL The row data of is flat , Each value in the row has a column . stay Mongodb Documents in can contain embedded subdocuments , So as to provide a closer internal data model for applications . stay Mongodb Records representing documents in are stored as BSON, This is a JSON A lightweight binary form of . Its fields / The value corresponds to Javascript Properties and values of . At the same time MongoDB The maximum size of the document in is 16MB. This prevents RAM Overuse or severe impact on the file system .

Besides , The field name of the document cannot contain (null) character 、 Period (.) Or the dollar sign ($)._id The field name is for the object ID Reserved . The _id Field is a unique in the system ID, It consists of the following parts :

1. One 4 Byte value , Represents the number of seconds passed since the era .

2. One 3 Byte machine identifier

3. One 2 Byte process ID

4. One 3 Byte counter , Start with a random value

5、 ... and 、Mongodb data type

Mongodb Each data type is assigned from 1 To 255 The integer of ID Number , You can use it to query by type .

Type description number

Double	Double precision value	1
String	character string	2
Object	object	3
Array	Array	4
Binary data	binary data	5
Object id	object ID	7
Boolean	Boolean value	8
Date	date	9
Null	Null value	10
Regular Expression	Regular expressions	11
JavaScript	Javascript	13
Symbol	Symbol	14
JavaScript(with scope)	Javascript( With scope )	15
32-bit intger	32 An integer	16
Timestamp	Time stamp	17
64-bit integer	64 An integer	18
Min Key	minimum value	255
Max Key	Maximum	127

When comparing different BSON Value of type ,Nongodb Use the following comparison order from lowest to highest :

1. Minimum key ( Internal type )

2. Null value

3. The number

4. Symbol 、 character string

5. object

6. Array

7. binary data

8. object ID

9. Boolean value

10. date , Time stamp

11. Regular expressions

12. Maximum key ( Internal type )

This is about MongoDB This is the end of the article on database basics . I hope it will be helpful for your study , I also hope you can support the software development network .