A database, as the name suggests, is a warehouse where data is stored. Only this warehouse is on a computer storage device and the data is stored in a certain format.

When people collect a large amount of data, they should save them into the near step of processing, further extraction of useful information. Back then, people stored data in filing cabinets, but now with the development of society, the amount of data has increased dramatically, and now people with the help of computers and database technology to save a large amount of data scientifically, in order to make better use of these data resources.

If the definition, it should be: refers to long-term storage in the computer, organized, **** enjoy the collection of data.

Database contains a relational database, object-oriented database and the emerging XML database, etc., the most widely used is the relational database, if the relational database on the basis of providing some of the object-oriented database functions of the object-relational database. In the early days of database technology was also popular hierarchical database and mesh database, but these two types of databases have been rarely used.

Database management

Database management (Database) is related to the establishment, storage, modification and access to information in the database technology, refers to ensure the normal operation of the database system and the quality of service, the relevant personnel to carry out the technical management work. Responsible for these technical management of the individual or collective known as the database administrator (DBA). Database management of the main content: the establishment of the database, database adjustment, database reorganization, database reconstruction, database security control, data integrity control and provide technical support to users.

Database Creation: The design of a database is simply a description of the data that provides the type, logical structure, associations, constraints, and storage structure of the data in question. These descriptions are called data schemas. To create a runnable database, the following tasks are also required:

(1) Select various parameters of the database, such as the maximum data storage space, the number of buffering decisions, concurrency, etc.. These parameters can be set by the user or by the system at default values.

(2) Define the database, using the data definition language and commands provided by the database management system (DBMS) to define the database name, data schema, indexes and so on.

(3) prepare and load data, define the database only to establish the framework of the database, to build the database must also be loaded with a large amount of data, which is a huge job. In the preparation and entry of data in the process, we must take measures in the technical and institutional measures to ensure the correctness of the data loaded. Computer system has been accumulated data, to make full use of, as far as possible to convert the database data.

Note: The word "database" for different people should give different feelings. If you're an end user, you don't care about the details of data storage and maintenance, and the database shouldn't bother you with those things. But if you are a database administrator, then there are some details that you have to be aware of. A database management system can provide different views to different users, which means that they don't see the same database. This requires data abstraction to form these different views.

The first three levels of data abstraction were given in full in the DBTG report of CODASYL.A similar recommendation was made in the ANSI/SPARC report, and the levels of abstraction in this report were internal, conceptual, and external. However, today's database management systems are abstracted from three levels based on the DBTG report, which are the physical, logical, and view (conceptual) layers.

Types of databases

Large databases are Oracle, Sybase, DB2, SQLserver

Smaller databases are Aess, MySQL, BD2, and so on.