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Database, relational database and NoSQL non relational database
2022-07-06 03:51:00 【Passerby Chen】
1. database (DataBase,DB)
database (DataBase,DB): It refers to the storage device stored in the computer for a long time ( Hard disk ) On , Organize according to certain rules , A collection of data that can be shared by various users or applications , Or in the form of files on the server computer .
database (DataBase,DB), Namely A warehouse for storing data , Data can be persisted , And pass sql Statement to quickly add, delete, modify and check the data CRUD operation (CRUDP: establish create, Read read, modify update, Delete delete, Pagination page).
The main difference between database and ordinary file system ( cause ): The database can quickly find the corresponding data .
database structure
A database server software can create multiple databases ( An application corresponds to a database )
A database can create multiple tables ( A class corresponds to a table )
A table can store multiple records ( An object corresponds to a record )
The client connects to the database server software
SQL(Structure Query Language, Structured query language )
SQL(Structure Query Language, Structured query language )), adopt sql Operating the database ( Operating the database , Operation table , Operational data ).
SQL By the National Bureau of standards (ANSI) American Standard for relational database language , Later, it was organized by international standards organization (ISO) International standards adopted as relational database language . Database manufacturers (MySql,oracle,sql server) All support ISO Of SQL standard . Each database manufacturer has made its own extension on the basis of the standard .
SQL The grammar of
Each statement ends with a semicolon ( The command line needs ), If in navicat,Java It is not necessary to add in the code .
SQL stay window Case insensitive in , In keywords, uppercase and lowercase are the same
SQL The classification of
DDL Data definition language | Data Definition Language | DDL Operating the database ,DDL Operation table |
DML Data manipulation language | Data Manipulation Language | DML Operation table record - Additions and deletions |
DQL Data query language | Data Query Language | DQL Operation table record - Inquire about |
DCL Data control language | Data Control Language | The setting of user rights |
2. Relational databases : Stored on disk
A relational database is a database created according to a relational model . The so-called relationship model is “ one-on-one 、 One to many 、 Many to many ” And so on , A relational model is a two-dimensional tabular model , Therefore, a relational database is a data organization composed of two-dimensional tables and their relations .
Relational models include data structures ( The problem of data storage , Two-dimensional table )、 Set of operation instructions (SQL sentence )、 Integrity constraints ( Table data constraints 、 Constraints between tables ).
Common relational databases
MySQL | Free open source , Small and medium-sized database | Has been Oracle Acquisition (MySQL6.X The version also began to charge ) |
OracleSQL | Rechargeable Large databases | Oracle Products of the company |
DB2 | Rechargeable In the banking system | IBM The company's database products |
SQLServer | Rechargeable Medium sized database | MS company |
SyBase | Has faded out of the stage of history | Provides a very professional data modeling tool PowerDesigner( Founder Wang Xiaoyun ) |
SQLite | Embedded small database | It's used on the mobile phone |
3. Non relational databases NoSQL(Not Only SQL): Stored in memory
NoSQL(Not Only SQL, meaning “ not only SQL”), It's a new database concept ( A general term for a non-relational database ), It is a supplement to relational database , Not a substitute .
effect : Dealing with data processing problems based on massive users and massive data .
NoSQL The advantages of :
1. Easy to expand
2. Large amount of data , High performance
3. Flexible data model
4. High availability
In order to solve the three high problems , That's what we need NoSQL
Three high questions :
1.High performance - High concurrent read and write requirements for database
2.Huge Storage - The need for efficient storage and access of massive data
3.High Scalability && High Availability- The need for high scalability and high availability of databases
Solve the bottleneck of relational database , Non relational data is currently used as a supplement to relational databases .
common NoSQL Non relational database
classification | Related products | Application scenarios | advantage | shortcoming |
---|---|---|---|---|
The key stores the database (Key-Value) | Redis、MemCache | Content caching , Like conversation 、 The configuration file 、 Parameters, etc. ; Read and write frequently 、 Applications with simple data models | Good scalability , Flexibility , High performance in a large number of operations | Unstructured data , It is usually only treated as string or binary data , The value can only be queried through the key |
Column family storage database ( Distributed ) | HBase、Cassandra、 Bigtable | Distributed data storage and management | High scalability , Fast search speed , Low complexity | Functional limitations , Strong consistency of transactions is not supported |
Document database <key,value> in value yes JSON Structured documents | MongoDB、CouchDB | Web application , Store document oriented or similar semi-structured data | Flexible data structure , According to value Build index | Lack of uniform query syntax |
graphics (Graph) database | Neo4j、InfoGrid | Social networks 、 Recommendation system , Focus on building the relationship map | Support complex graphics algorithms | High complexity , It can only support a certain data scale |
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