Database basic concept of database series

Database-related concepts

1 data: Symbols that describe things.

2 database: The warehouse where the data is stored.

3 Database Management System: The program that manages the database.

4 database administrator: The person who manages the database.

5 Database system: Database-related hardware (CPU, memory, hard disk, etc.), software (operating system, database management system, etc.) and person (DBA).

6 data Model: The storage structure of data in a database.

I understand the database

If there is a library, the library has 10 bookshelves, the 10 shelves of science, running, biological, physical, chemical books, and each bookshelf each row only stores one writer's books, each column is the book publication date. Therefore, I understand the database is the library, the table is a bookshelf, I want to find a book, just find the author of the book and the corresponding publication date, naturally know the book in which cell.

Database History 1 Hierarchical model

is a tree structure, which consists of nodes and lines, where nodes represent entities and lines represent relationships between entities.
You can list the case of the department. It contains the number of majors, which classes are included under each specialty, and which students are in each class. At the same time, there are various associations within the Department, the members of the community (the members of the community are actually students, then the students in the class and the students in the community are repeating). The longitudinal development of data, but the horizontal relationship is difficult to establish. Data duplication occurs.

2 Mesh Model

Data records form a node in the network, and the association between Records and records forms a connection between nodes, thus constituting a complex network structure.
Advantages:
(1) It is easy to reflect the relationship between entities, each record includes not only its own information but also the location of the relevant information description.
(2) Avoid the duplication of data.

3 Relationship Model

The storage structure used is multiple two-dimensional tables. In a two-dimensional table, a row represents a record that describes an object's information, and a column becomes a field that describes an object's properties.

4 Object-oriented model

The combination of object-oriented thinking and database technology can make the analysis and design of data system consistent with people's understanding of the objective world.

Advantages:

(1) Scalability and extensibility, dealing with complex data models and relational models.

(2) Using the method of inheritance to realize the reuse of data and avoid data redundancy.

(3) Improve the description, manipulation and retrieval ability of large object (text, image, video) information.

Disadvantages:

(1) Lack of the theoretical basis of solid maturity like relational data model.

(2) Poor operating efficiency.

relational database

A relational database is a collection of data and database objects.

Data tables, rows (records), Columns (fields), entities, properties.

The storage structure used is multiple two-dimensional tables.

In a two-dimensional table, a row represents a record used to describe the information of an entity (object);

A column becomes a field used to describe an attribute of an entity (object).

Database basic concept of database series