What is a database? What the hell is Oracle Bone Inscriptions?

People often ask me what the database is for. In fact, I refused to answer at first, because I was not easy to express. After all, I haven't been exposed to this concept for a long time, but with more people asking, I think it's time to make up my first class. If one day a product comes out and you don't explain it to him for minutes, it will be embarrassing for a loser at last.

Database, to put it bluntly, is a warehouse that organizes, stores and manages data according to data structure. These data are structured and can be used in various applications. In other words, a database uses a computer server to store data and is dedicated to providing various data services. As you can imagine, in the past, all the financial data of a company were put in the safe, but now we can build a database for these financial data and put it on the computer or server; For another example, the personnel department of enterprises and institutions often stores the basic information of employees (job number, name, age, gender, place of origin, salary, resume, etc.). ) in a table, can be regarded as a database. With this "data warehouse", we can query the basic situation of an employee at any time as needed, and we can also query the number of employees whose wages are within a certain range, and so on. If all these tasks can be done automatically on the computer, then our personnel management can reach a very high level. In addition, in financial management, warehouse management and production management, it is necessary to establish many such "databases" in order to realize the automatic management of finance, warehouse and production by computer. The most common databases are: bank savings system, mobile phone billing system, beauty salon membership system, supermarket membership points system, water and electricity system, air ticket or train ticket system, etc. These all need the support of the background database infrastructure. With so many examples, we should make the database clear, at least we can have a concept in our mind and know what this thing is for.

Now big data has been fired to purple, and the foundation of big data is also data. It can be seen that data is the core resource of an enterprise, and it is not an exaggeration to say that it is the foundation of the enterprise's foundation and development. Therefore, the database administrator (DBA) who maintains the database is indispensable for enterprises.

At present, there are many database products on the market, which can be divided into three types: large, medium and small. Typical database products are as follows:

Large databases: Oracle, DB2, Sybase.

Medium-sized databases: MySQL, SQLServer, Infomix.

Small database: Access. Among many database products, Oracle database has been in the leading position in the industry, and it is also the most popular relational database today. Oracle Bone Inscriptions can be translated as "Oracle Bone Inscriptions". Is a global company with database as its main business, and the second largest software company in the world (the first is Microsoft). At present, Oracle has ranked first in the database software market, with a market share of 48.6%, far ahead of the second IBM DB2 with a share of only 20.7%. In China market, most of the databases used in the background of computer professional systems are Oracle databases. However, it costs a lot of money to buy an Oracle database. Generally, large enterprises need professionals to manage and maintain, and small and medium-sized enterprises can't afford it. In order to save costs, small and medium-sized enterprises generally use free and open source databases such as MySQL and PostgreSQL, so the work related to Oracle database is generally in large enterprises.

Why choose Oracle database over other databases?

First, because Oracle database occupies the largest market share, and it is getting bigger and bigger, the market needs a large number of talents in Oracle database. There is an old saying in China that "do the right thing and choose the right person", which is also the truth; Second, many old systems that are not Oracle databases are migrating to Oracle databases, and the market share of other databases is decreasing, so other database workers are facing the risk of unemployment; Thirdly, Oracle has a large number of official learning documents and some Chinese documents, which can be used for effective learning; Fourth, there are many employees in Oracle Bone Inscriptions, and friends in the same direction can help each other, and they are no longer lonely heroes; Fifth, you can easily download the latest version of the full-featured database from the official website of Oracle for learning, which can let you know the latest development trend of the database.

Everything here is based on Oracle 1 1g database products. First, briefly introduce the series products of Oracle 1 1g:

EnterpriseEdition This version contains all the components of the database and can be further enhanced by purchasing options and software packages.

For example, it can support on-line transaction processing environment with large business volume, query-intensive data warehouse and demanding Internet applications.

Standard Edition 1(StandardEditionOne) This edition provides unprecedented ease of use and cost performance for workgroup, department, Internet and intranet applications. From a single server environment in a small business to a large distributed departmental environment, this version contains all the tools needed to build important business applications. It is only allowed to be used on servers with a maximum capacity of 2 processors. It supports Windows/Linux/UNIX operating systems and 64-bit platform operating systems.

StandardEditionThis version provides ease of use, functions and performance that StandardEdition does not have, and provides support for larger computer and service clusters by using real application cluster (RAC). It can be used on a single server with a maximum capacity of 4 processors or on a cluster with a maximum capacity of 4 processors. It can support Windows, Linux, UNIX operating systems and 64-bit platform operating systems.

Simplified version This version supports single-user development and deployment, and is fully compatible with standard version 1, standard version and enterprise version. By introducing the award-winning functions of Oracle database into personal workstations, this version provides a database that combines the most popular database functions in the world. This database has the usual usability and simplicity of desktop products, and can support Linux and Windows operating systems.

As far as storage structure is concerned, currently popular databases mainly include the following two types:

RDBMS: Relational database refers to a database that uses relational models to organize data;

NoSQL databases refer to those non-relational and distributed databases. Simply put, a relational model refers to a two-dimensional table model, and a relational database is a data organization composed of two-dimensional tables and their relationships.

Advantages of relational database:

1, easy to understand

Two-dimensional table structure is a concept very close to the logical world, and relational model is easier to understand than other models such as grid and hierarchy.

2, easy to use

The common SQL language makes it very convenient to operate relational databases.

3, easy to maintain

Rich integrity greatly reduces the probability of data redundancy and data migration.

4. Transaction security

All relational databases abide by the four basic attributes of things to varying degrees, so they are indispensable for transactional businesses such as banking, telecommunications and securities.

Bottleneck of relational database;

1, high concurrent read and write requirements

The user concurrency of the website is very high, often reaching tens of thousands of read and write requests per second. For traditional databases, hard disk I/O is a big bottleneck.

2. Efficient reading and writing of massive data

The amount of data generated on the Internet every day is enormous. For relational databases, it is very inefficient to query in tables containing massive data.

3. High scalability and availability

In the web-based structure, the database is the most difficult to expand horizontally. When the number of users and visits of an application system are increasing day by day, the database cannot simply expand its performance and load capacity by adding more hardware and service nodes (such as WEB Server and APPLICATIONServer). For many websites that need to provide 24-hour uninterrupted service, it is very painful to upgrade and expand the database system, which often requires downtime maintenance and data migration.

NoSQL database

The word NoSQL was first put forward by CarloStrozzi in 1998. In 2009, the word NoSQL was put forward again, which refers to those data storage systems that are non-relational and distributed and generally do not guarantee to follow the ACID principle.

NoSQL has the following characteristics:

1 can make up for the deficiency of relational database.

2, designed for some specific needs, can have extremely high performance.

3. Most of them are open source. Because it is not mature enough, there are potential stability and maintainability problems.

Relational database is suitable for structured data, while non-relational database is suitable for unstructured data. Their advantages complement each other.

The future development direction of Oracle database is to provide structured, unstructured and semi-structured solutions to realize the complementarity between relational database and NOSQL. It is worth emphasizing that relational database is still the mainstream database at present.

Although NoSQL database breaks the concept of relational database storage and can meet the data storage requirements in the WEB2.0 era, it also has its own defects. At this stage, relational database and NoSQL database can be combined to make up for each other's shortcomings.

So much for today about database and its representative product Oracle. Those who are interested can continue to dig deeper. I hope my introduction will give you a deeper understanding of the database. If you are interested in developing in this field, let's drink to the past and start all over again.