Getting Started with databases 1 understanding databases

Knowledge Content:

1. Overview of database Technology

2. Development of database technology

3. Introduction to the Mainstream database

I. Overview of database Technology

1. What are databases, database management systems, database systems

Database (DB): A database is a collection of organized, shareable data that is stored in a computer for a long period of time

Database management System (DBMS): A database management system is a software system that is responsible for the definition, establishment, operation, management and maintenance of database.

Database System (DBS): The database system is a system of computer software, hardware and data resources that are organized and dynamically stored to facilitate multiuser access to a large number of associated data.

2. Introduction to the database system

(1) Classification of database systems

Depending on the system structure of the computer, DBS (database system) can be divided into 4 categories: centralized, customer \ Service, parallel and distributed

(2) Database system components

A typical database system should include database, hardware, software (application) and database Administrator (DBA) 4 parts, the narrow-sense database and database management system together constitute the database system

(3) Characteristics of the database system

• The data in the database system is structured
• Data redundancy is small and easy to expand
• High data and program independence
• The database provides a convenient interface for users
• The smallest unit of data is the data item

(4) Control function of database system

• Data security controls to prevent data leaks and corruption
• Correctness, validity, and compatibility of data with integrity constraints
• concurrency control, which prevents multiple users from accessing and modifying data in the database at the same time, interferes with data integrity and damages
• Database recovery is required in case of database failure

Second, the development of database technology

1.web Application Development Technology Brief introduction

(1) CGI Programming--now no longer exists.

CGI (Common Gateway Interface) is a communication standard whose task is to accept requests from clients, be identified and processed, generate HTML documents, and re-route them to the client. The programming of this interactive process is called Universal Gateway Interface programming. CGI can be run on multiple platforms, and CGI programs can be written in multiple languages, but there are also fatal drawbacks: slow speed, poor security

(2) Asp

ASP (Dynamic Server Page) is a Microsoft company introduced to replace CGI technology, is easy to learn, powerful server programming technology. With ASP, dynamic, interactive and efficient Web server applications can be built. The program written by ASP is executed on the service side, and the execution results are returned to the client browser after the execution of the program, which not only relieves the pressure of the client browser, but also greatly improves the interaction speed, and avoids the leakage of the source code of the ASP program, and improves the security of the program.

(3) Jsp

JSP (Java Server page) is Sun's launch of Web application development technology, once launched on the big attention. JSP Technology uses the Java language to write server-side programs, and when a client requests a server, the JSP source program is compiled into a servlet and executed by a Java virtual machine. This compilation occurs only on the first request to the JSP page, so the JSP program provides faster interaction speeds, security and cross-platform excellence

2. Development of database Technology 3 major stages

(1) Artificial management stage

Until the 1950s, The computer is mainly used for numerical calculation. From the time of the hardware, external memory only tape, cards, tapes, no direct access to equipment, from the software (in fact, not yet formed the overall concept of software), no operating system and the management of data software; From the data, the data is small, the data is unstructured, directly managed by the user, and the data For specific applications, lack of independence

(2) File system phase

In the late 50 and mid-60, there were drum, disks and other data storage devices. The new data processing system has developed rapidly. This data processing system is the computer in a separate data file, the system can be accessed according to the name of the file, access to the records in the file, and can implement the file modification, insertion and deletion, this is the file system. The file system realizes the structure of the record, The relationship between the various data in the record is given. However, the overall view of the file is unstructured. Its data is targeted to specific applications, so data sharing, independence, and redundancy, and the cost of management and maintenance are significant

(3) Database system phase

In the late 60, data management technologies such as databases emerged. The database is characterized by the data is no longer only for a specific application, but for the whole organization, with overall structure, high sharing, redundancy is small, with a certain degree of independence between the program and data, and achieve a unified control of the data

Three, the mainstream database introduction

1.SqlServer

(1) SQL Server Introduction

SQL Server is a database developed and promoted by Microsoft and is a widely used database management system

(2) SQL Server pros and cons

Advantages:

• Ease of Use
• Scalability for distributed organizations
• Data Warehouse features for decision support
• Integration that is closely associated with many other server software
• Good value for money

Disadvantages:

• Openness: can only be run on Microsoft's Windows platform, without the slightest openness to speak of
• Scalability and parallelism: the parallel implementation and coexistence model is immature and difficult to handle the increasing number of users and data volumes with limited scalability
• Performance Stability: SQL Server performance can become poor and unstable when users connect for a long time
• Use style: SQL Server completely rewrites the code, undergoes long-term testing, is constantly delayed, and many functions take time to prove. is not very compatible with earlier products. Use requires a certain risk
• Client Support and Application mode: only support C/s mode

2.MYSQL

(1) MySQL Introduction

MySQL is a relational database management system developed by the Swedish MySQL AB company and is currently part of Oracle's product portfolio. MySQL is one of the most popular relational database systems, and in WEB applications MySQL is the best RDBMS (relational database Management system, relational databases management systems) application software

In addition, because of its small size, fast speed, low total cost of ownership, especially the development of the source of this feature, the general development of small and medium-sized web site to choose MySQL as a Web database. Thanks to the excellent performance of its community edition, it is a good development environment with PHP and Apache

(2) MySQL pros and cons

Advantages:

• Small size, fast speed, low total cost of ownership, open source supports multiple operating systems
• is an open source database that provides interfaces that support multiple language connection operations
• The core program uses full multithreaded programming. Threads are lightweight processes that provide the flexibility to service users without excessive system resources
• Supports ODBC for Windows, supports all ODBC 2.5 functions and many other functions, can connect to MySQL server with access, so that the application is extended
• Support large database, can easily support the database of thousands record. As an open source database, it can be modified for different applications.
• Have a very fast and stable thread-based memory allocation system that can continue to use polygons without worrying about their stability
• MySQL offers a wide variety of different user interfaces, including command-line client operations, Web browsers, and a variety of programming language interfaces.
• Cross-platform, can be used on Windows, Linux, Unix, Mac

Disadvantages:

• Hot Backup not supported
• MySQL's biggest drawback is its security system, which is mostly complex rather than standard, and only changes when Mysqladmin is called to reread user rights.
• There is no stored procedure (Stored Procedure) language, which is the biggest limitation for programmers accustomed to enterprise-grade databases

3.oracle

(1) Oracle Introduction

Oracle is a relational database management system of Oracle Corporation. It is a leading product in the field of database. It can be said that Oracle database system is currently the world's popular relational database management system, System portability, easy to use, strong function, applicable to all kinds of large, medium, small, microcomputer environment. It is a highly efficient and reliable database solution for high throughput

(2) Oracle Pros and cons

Advantages:

• Openness: Oracle can run on all major platforms (including Windows) fully supports all industry standards with fully open policies enabling customers to choose the right solution for the developer's full support
• scalability, parallelism: Oracle parallel servers extend WINDOWNT capabilities by enabling group nodes to share the same cluster work to provide high availability and high scalability
• Security: ISO standard certification for the highest level of certification
• Performance: Oracle performance remains open platform tpc-d and Tpc-c world records
• Client Support and Application Mode: Oracle Multi-level network computing supports a wide range of industrial standards such as ODBC, JDBC, OCI and other network customer connections
• Use risk: Oracle's long-time development experience is completely backwards compatible with low risk of widespread application

Disadvantages:

• High Requirements for hardware
• The price is more expensive
• Management Maintenance Trouble Some
• Operation is more complex, need high technical content

4.db2

IBM DB2 is a relational database management system developed by IBM in the United States, and its main operating environment is UNIX (including IBM's own Aix), Linux, IBM i (formerly known as os/400), z/OS, and Windows Server version

5.MongoDB

MongoDB is a database based on distributed file storage. Written by the C + + language. Designed to deliver scalable, high-performance data storage solutions for Web applications

MongoDB is a product between relational database and non-relational database, which is the most abundant and most like relational database in non-relational database. The data structures he supports are very loosely structured, like the Bson format in JSON, so you can store more complex data types. MONGO's biggest feature is that his supported query language is very powerful, its syntax is a bit like object-oriented query language, almost can realize the most functions like relational database single table query, but also support the indexing of data

6.Redis

Redis is an open source API that is written in ANSI C, supports the web, can be persisted in memory, key-value databases, and provides multiple languages. From March 15, 2010 onwards, the development work of Redis is hosted by VMware. Since May 2013, the development of Redis has been sponsored by pivotal. Redis Read and write data is very efficient, far more than the database, because the Redis exchange of data fast, so in the server is often used to store some of the data need to be frequently transferred, which can greatly save the system to read the disk directly to obtain the data I/O overhead, more importantly, can greatly improve the speed

Getting Started with databases 1 understanding databases