What are the types and characteristics of databases?

Database classification:

There are three early database models , respectively hierarchical database, network database and relational database.

In today's Internet, databases are usually divided into two categories, namelyrelational databases and non-relational databases.

Relational database and examples:

Relational database refers to a database that uses a relational model to organize data, and relational A model is a data organization consisting of two-dimensional tables and their relationships.

Features:

Advantages:

1. Easy to maintain: they all use table structure and have the same format;

2. Easy to use: SQL language is universal and can be used for complex queries;

3. Complex operations: Supports SQL and can be used for very complex queries between one table and multiple tables.

Disadvantages:

1. Poor reading and writing performance, especially high-efficiency reading and writing of massive data;

2. Fixed table structure, slightly less flexible;

3. High concurrent reading and writing requirements. For traditional relational databases, hard disk I/O is a big bottleneck.

The current mainstream relational databases are:

MYSQL

The most widely used open source, multi-platform relational database Type database, supports transactions, is compliant with ACID, and supports most SQL specifications

SQL Server

supports transactions, is compliant with ACID, and supports most SQL specifications. It is a commercial software, so please note Copyright and license authorization fees

Oracle

supports transactions, complies with relational database principles, complies with ACID, supports most SQL specifications, and is the most powerful and complex in the market The commercial database with the highest proportion

Postgresql

Open source, multi-platform, relational database, the most powerful open source database, requires python environment, TimeScaleDB based on postgresql , is one of the more popular time series databases at present

Non-relational databases and examples:

Non-relational databases are also called NOSQL (Not Only SQL ), as a supplement to the relational database,can exert high efficiency and high performance in specific scenarios and characteristic problems.

Common non-relational database types include key-value (Key-Value) storage database and document-oriented database (Document-oriented)

Key-value storage database is similar to hash, adding through key, Deletion, query, high performance, the advantages are simplicity, easy deployment, and high concurrency.

The main products are:

Redis

Open source, Linux platform, key-value key-value Nosql database, simple and stable, very mainstream, Full data in-memory, key-value nosql database positioned as "fast"

Memcaced

An open source, high-performance, distributed memory object Caching system, through which the database load can be reduced and dynamic web applications can be accelerated.

Document-oriented databases are stored in the form of documents. Each document is a collection of a series of data items. Each data item has a name and a corresponding value.

MongoDB

Open source, multi-platform, document-based NoSQL database, "most like a relational database", positioned as a "flexible" NoSQL database. Suitable for website backend database (fast update, real-time replication), small file system (json, binary), log analysis system (files with large data volume)

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