Summary of database principles,

Source: Internet
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Summary of database principles,

Summary of database principles

Database technology is a technology that mainly studies how to scientifically organize and store data, efficiently obtain and process data, and meet different information needs of users, because of the large demand for database technology, it is necessary to learn the knowledge and technology of this course. You should be familiar with the knowledge of data, data management, database, the connotation of professional terms such as data model and concept model.

Chapter 1 Introduction

1. Master the concepts of databases, database management systems, and database systems (components)

2. Understand the three phases of database technology development

3. Master the concept of Level 3 mode and level 2 Image

4. Understand the main functions of the Database Management System

Knowledge point:

Data:The object of research and processing by the database system, which describes the symbolic records of world things,It has the following four features:

1: Data has "value" and "type"

"Value" refers to the specific data value, and "type" refers to the data structure.

2: Data is restricted by the value range and type.

3: either qualitative or quantitative representation.

4: it has a carrier and multiple forms of expression.

Database:A set of data that has been stored in a computer for a long time and is organized, shared, and centrally managed. It is a computer software system that stores data according to the data structure.

1: new methods and technologies for data storage and management can organize data more rationally, facilitate and rationally maintain, control, and utilize data.

Features of a data set:

1: Minimum Redundancy.

2: applications share data resources.

3: high data independence.

4: unified management and control.

Database Management System (DBMS ):Provides computer software for data management.

Implements unified management and control over the database to ensure the security and integrity of the database. Users can access the database content through the DBMS, and the database administrator can maintain data through the DBMS..

Main functions:

1: Data Definition capability.

2: Data manipulation capability.

3: database maintenance capability.

4: database creation and maintenance functions.

Database System:

A computer system that includes computer hardware, databases, database management systems, application systems, and database administrators, and carries databases and uses database technology for database management.

Compared with the file system, the database system has the following features:

1: structured data.

2: The database system features low data redundancy and high data sharing.

3: Data and programs in the database system are highly independent.

4: The minimum unit for data access in the database is data items.

5: unified data management and control.

6. Provide database protection.

Chapter 2 Data Modeling

1. Grasp the representation of the object contact model (E-R diagram), including the entity, attribute, contact and contact type.

2. Understand the three elements of the data model

3. Understand the characteristics of hierarchical and mesh Data Models


Common Database models: 1. Hierarchical Models:

2. mesh model, 3. Relational Model, and 4 object-oriented model.

1. Entity)
An entity is an object that exists objectively in the real world. It can be a specific thing, such as a house, an element, a person, or an abstract thing, such as an idea, a plan, or a project. Entities are represented by their own property values. Entities are divided into strong and weak entities.

2. entity set:
A collection composed of entities with the same structure and characteristics is called an entity set. For example, Student Entity set and class entity set.

3. Object Type:
Describes the information structure of an object set, usually including a set of type names and object attribute names. For example, student (student ID, name, gender, age, class ).
4. attributes:
Describes the characteristics of an object or link. Each feature of an object is called an attribute. Attributes include attribute name, attribute type, attribute definition field, and attribute value.
5. entity ID (code or key ):
The value uniquely identifies an object's property set. The identity of an entity in a relational database is called a code or key. Its identity code is the value of a single attribute or a subset of an object.
For example, a student's student ID is both a student's attribute and a student's identity code. The student ID can be the name or number of the Institute.
6. Contact:
In the real world, the interconnectivity between things exists objectively, and the connection reflects the interconnectivity between entities. This relationship must be described in the information world. Besides being used as an attribute, a contact can also have a property value.
For example, each teacher belongs to a research institute, and each teacher has a affiliation relationship with a research institute.
7. Contact set:
Links of the same type between entities also constitute a contact set. For example, a consortium is formed between multiple teachers and their affiliated institutes.
8. Contact Type:
Describes the information structure of the contact set between entities with common characteristics, including the type name and attribute of the contact.
For example, each teacher is "affiliated" with a research institute, and each teacher is connected with the students it teaches; there is a "supply" link between the parts supplier and the parts it supplies, and the "supply" link has the supply quantity attribute.


· Data ):
Symbols that reflect the facts of the objective world and distinguish their characteristics: characters, numbers, texts, sounds, figures, images, charts, pictures, etc., which exist objectively in the real world, which can be input to the computer for storage and management.
· Information ):
Data that is processed and extracted from raw data and used to determine behaviors, plans, or have certain semantics is called information.
· Database DB (Data Base ):
It is a collection of highly correlated data and relationships in the real world.
· Database Management System (DBMS ):
Is a software system that stores and manages data in databases. It includes various languages and tools for storing, managing, retrieving, and controlling data in databases. It is a set of system software.
· Database System DBS (Data Base System ):
Is a general term for database and database management systems. It refers to a collection of associated data and a collection of software tools that manipulate data. DBS = DB + DBMS
· Application Programming Interface ):
It is an interface function, process, or language provided by DBMS for developing applications to manipulate and access data in the database.
· Database Application AP (Application Program ):
A program that allows users to manipulate and access databases.
· Data Warehouse)
A data warehouse is a commercial application system with built-in databases. Use existing data resources to convert data into information, extract knowledge from it, extract it into wisdom, and create benefits.
· Data Mining)
Data mining can help commercial users process a large amount of existing data in order to discover "unexpected relationships" to increase market share and profit.
· Information Mining ):
Information Mining refers to discovering relevant information in the vast ocean of documents, maps, photos, sounds and images, that is, content-oriented retrieval.
· Data Model ):
In a database, the description of data (entity) is called the database mode. It is described in the corresponding Schema Definition Language.
· Data Model ):
It is a digital simulation and abstraction of real-world features.
· Field ):
The smallest unit of data in a hierarchical data model, which describes the attributes of an object.
· Segment ):
It is the unit of Entity description in the IMS layered data model and a record composed of a field set. It is also the unit in which applications access database data.
· Data Item ):
It is the smallest data unit in the mesh data model named by DBTG, indicating the attributes of an object.
· Record ):
It is the unit of Entity description in the mesh data model named by DBTG and an ordered set of data items.

· Domain ):
The field is a set of values, that is, the value range.
· Relationship ):
A link is a two-dimensional table with a table name.
· Tuple ):
A row in a relational table is called a tuples. Tuples can indicate the relationship between an object or an object.
· Attribute ):
A column in a relational table is called an attribute of a link, that is, a data item of a tuples. Attributes include attribute name, attribute type, attribute value range, and attribute value. The attribute name is unique in the table.

· Keywords (Primary Key ):
A single attribute or a combination of several attributes in a table, and its values can uniquely identify a tuples in a link. The keyword attribute cannot be null.
· External keywords (Forgien Key ):
An Attribute Group that corresponds to a keyword of another link is called an external keyword of the link. The external keyword is null or the key value corresponding to the External table.
· Network Library ):
A communication software package that packs database requests and results, which are transmitted over the network protocol. Net-Library must be installed on both the client and server.
Chapter 1 Relational Database

2. Understand the six properties of a link

3. grasp the concept: Representation of codes, primary attributes, non-primary attributes, full codes, and external codes, and relational modes.

4. Master the three types of integrity constraints of the Link (entity integrity, reference integrity, and user-defined integrity)

5. Familiar with relational algebra to express various types of queries (set calculation, selection, projection, join, Division); able to express query requirements based on the data table structure and relational algebra.

Knowledge point:Data conceptual model:

E-R Diagram:

For example:

UML Model:

There are usually four types:

1: hierarchical model.

2: mesh model.

3: relational model.

4: object-oriented model.

Chapter 1 Standardization Theory

1. grasp the concept: function dependency, partial function dependency, full function dependency, and transfer function dependency.

4. grasp the concept of paradigm: 1NF, 2NF, 3NF

5. Master the decomposition methods and steps of the pattern; be able to judge its paradigm type based on the given relational pattern, and break it down as required to reach the specified paradigm level.

6. Understand the principles of link Mode Decomposition

Chapter 2 Database Design

1. Understand the six steps of database design and the methods used

3. Master the conceptual structure (E-R diagram) design method, understand the common three kinds of conflicts between each E-R Diagram

4. Master the rules of converting E-R diagram to relational mode, and understand the optimization of data model.

Based on the given semantics, we can find the relevant entities, the attributes of the Entities, the relationship between the entities, draw a E-R diagram, and can be converted to the corresponding relationship pattern.

Chapter 2 SQL language

1. Data Definition Language, Data Query Language, and data update Language

2. Concepts of indexes and views

Write SQL statements based on the given table structure and query requirements.

 Chapter 2 database security protection (non-important chapter)

1. Understanding concepts: Features of transactions and transactions

2. Understand the concept and common methods of security control, and master the basic statements for granting and revoking permissions.

3. Understand the concept of integrity control

4. Understand the concept of concurrency control and inconsistency of the three types of data caused by concurrency

Understand the concept of blocking and the blocking Protocol

 5. Understand the concept and principle of database recovery

Temporarily update to this, and add the rest tomorrow.

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