About sql+nosql: newsql database

One 、 What is a database ？
Generally a database system （Database System） It can be divided into two parts ：

1. database （Database）

2. data management system （Database Management System,DBMS）

• A Database is an organized collection of data. —— Wikipedia database Namely Organized data sets , Stored in one or more disk files , Be commonly called 「 Warehouse of data 」. Broadly speaking , Anything that can store data can be counted as a database （ Such as txt file 、Excel Forms, etc ）.

• Database Management Systems (DBMS) data management system Namely Application software for operating and managing database , For building 、 Use and maintain database （ Persistent storage 、 Optimize reading and writing 、 Ensure the effectiveness of data, etc ）.
  In a narrow sense , What we say “ database ”, Usually it means 「 Database management system (DBMS)」.
  Two 、 Why use a database ？
  1. If the data is saved in memory ：

• advantage ： Very fast reading and writing

• shortcoming ： Data loss due to program shutdown 2. If the data is saved to the file system ：

• advantage ： Data can be stored permanently

• shortcoming ：1. Frequently IO operation , The efficiency is not high ;2. Data management is not convenient , If you want to query a certain data, you need to read it all , Match again . 3. If the data is saved in the database ：

• Persistent storage of underlying data

• Ensure the consistency and stability of the underlying data

• It provides an interface to operate and retrieve data

• Support SQL sentence , Can be used for complex queries

• Facilitate the daily maintenance and management of data

• Finer grained control and rendering than ordinary file systems

• You can use the read-write interface of the database in the program

• It provides concurrency control access and data fault tolerance mechanism
  .... A thousand words a word ： convenient 、 efficiency 、 Security
  3、 ... and 、 What databases are there on earth ？
  Database popularity ranking ：

  

• Database layout

  

  1. Relational database (RDBMS)

• Relational Database Management Systems (RDBMS) Relational database (RDBMS) It's a database based on a relational model , With the help of set algebra and other mathematical concepts and methods to deal with the data in the database , It is the most widely used database management system at present .
  「 Father of relational database 」 Edgar · frank · Codd (Edgar Frank Codd, 1923-2003) brief introduction

• In a relational database , There are mainly the following nouns ：

1. database ： Set of tables

2. Data sheet ： A collection of data

3. data row ： A row of data is an object

4. Data columns ： Also called field , Represents the properties of an object

• A relational database is like a Excel file , In the document sheet It's like a watch ,sheet The logical definition of each column in the table is the field of the table ,sheet The middle row is the data row of the table .

• Representative products of relational database ：

database	brief introduction	Application scenarios
Oracle	Because it was born early 、 Rigorous structure 、 High availability 、 High performance 、 High safety and other characteristics , Make it almost monopolized in traditional database applications , Finance 、 signal communication 、 energy 、 logistics 、 retail 、 Large companies in various traditional industries such as manufacturing are using , Even the early world 500 Strong enterprises are almost all Oracle Users of .	Mainly in the data-based business of traditional industries , such as ： signal communication 、 Bank 、 The availability of such finance 、 Robustness, 、 Security 、 Business with high real-time requirements ; Or retail 、 logistics 、 Energy is a business with high requirements for massive data storage and analysis . Usually with Oracle Large servers and disk arrays use , The price is very expensive .
MySQL	Web The most widely used relational database in the era ,MySQL The main application scenario of early positioning is Internet development . so to speak , It is the explosion of the Internet that has made MySQL,LAMP Architecture is popular all over the world . And because the MySQL More pursuit of light weight 、 Easy to use , In the traditional database application scenario , Very little share .	Most of its application examples also focus on the Internet ,MySQL The high concurrent access capability of is no worse than that of large databases , At the same time, the price is cheap , Easy to install and use , Deeply loved by the majority of Internet companies . And because of MySQL Open source features of , For some applications with special requirements for database , Directional optimization can be achieved by modifying the code , For example, Taobao .
Microsoft SQL Server	yes Microsoft An important part of the company's software integration program , Because only in Windows Upper use , Not as popular as the first two . General configuration ASP.Net Development , Also for the Windows The popularity of the system in enterprise applications has made a great contribution .	Microsoft SQL Server Mainly for small and medium-sized enterprises . Its biggest advantage is that it integrates MS All kinds of products and resources of the company , Provides a powerful visual interface 、 Highly integrated management development tools . It also provides a complete set of software solutions , Basically a set Windows The system will live after it is installed . therefore , Not so short of money , But it's scarce IT Small and medium-sized enterprises with talents , Will prefer Microsoft SQL Server .

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• The era of big data is coming , Disadvantages of relational databases ：

1. The processing data format is single ： The two-dimensional tabular data model used in relational database can not effectively deal with multi-dimensional data , Can not effectively deal with semi-structured and unstructured massive data in Internet applications , Such as Web page 、 E-mail 、 Audio 、 Video etc. .

2. High concurrent read / write performance is low ：Web2.0 The concurrent load of the website database is very high , Often tens of thousands of read and write requests per second . Relational databases can barely cope with tens of thousands of times SQL Inquire about , But hard disk I/O Often can not afford tens of thousands of times SQL Write data request .

3. Low scalability ： When the number of users and visits of an application system increases day by day , The traditional relational database has no way like Web Servers simply add more hardware and service nodes to expand performance and load capacity . For many systems that need to provide uninterrupted service , Upgrading and expanding the database system often requires downtime maintenance and data migration . According to this situation ,NoSQL Technology came into being .

   2. Non relational database (NoSQL)

• Originally referring to "non SQL", "non relational" or "not only SQL" (NoSQL)NoSQL It generally refers to non relational databases . Is different from the traditional relational database database management system .NoSQL The production of database is to solve the problem of large-scale Data sets The challenge of combining multiple data types , Especially big data application problem .

• NoSQL Main advantages over relational databases ：

1. Low latency reading and writing speed ： Rapid application response can greatly improve the speed of user interaction ;

2. High performance and scalability ： Based on key value pair , The data is not coupled , Easy for distributed expansion ;

3. Unstructured and unpredictable data ：NoSQL The storage format is Key-Value form 、 Document form 、 Picture form and so on , Relational databases only support basic types .

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• NoSQL It is very popular in recent years , Divided into four categories ：

1. Key value type (Key-Value)
   Redis、 Riak Content caching , It is mainly used to deal with intensive processing of large amounts of data IO High load access .
   The key value database is the simplest form NoSQL, Every value in the data （value） There are special keys （key） To match , It can achieve ultra fast application performance for relatively simple data sets , Search speed is very fast .

2. Document type (Document)
   MongoDB、 CouchDBWeb application , Collect and process data from web pages and mobile applications .
   Document databases store data in a document like structure , It can take the form of modeless , Data structure requirements are not strict , Variable table structure .

3. Column store (Big tables)
   HBase、 Cassandra Usually used in Internet search 、 Other large-scale web applications and PB Analysis and application of level data .
   Store as a column cluster , Store the same column of data together , When dealing with large data sets , You can have higher performance and scalability （ Such as HBase+Hadoop framework ）.

4. graphics (Graph)
   Neo4J、 GraphDB Social networks , Recommendation system, etc , Focus on building a relationship map .

A structure similar to a graph stores data , You can use graph structure related algorithms , Easy to explore the connection between data .

• NoSQL The shortcomings of ：

1. I won't support it SQL sentence ： Does not provide SQL Support , The cost of learning and using is high ;

2. The functionality provided is limited ： No transactions , The complete solutions and reports are not well supported ;

3. stability ： The perfection and stability of the product , It cannot be compared with the relational database with decades of history . 3. SQL+NoSQL : NewSQL
   NewSQL Database is an open source software product , Compared with traditional relational database and NoSQL, It can use SQL Statement to query data , At the same time, it has modern , Distributed , High fault tolerance , Cloud based cluster architecture .
   NewSQL Combined with the RDBMS Rich and flexible data interaction ability and stability and management mechanism , It can also provide NoSQL Real time expansion capability for big data and fast data .
   About SQL+NoSQL : NewSQL database _weixin_33754065 The blog of -CSDN Blog

author ： Zhishou

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