Concepts on Database books

Read the database and extract some concepts,

 

Database

 

Chapter 1 Introduction

 

Data: basic objects stored in databases

 

A database is a collection of large data that has been stored in a computer for a long time and can be shared.

The data in the database is organized, described, and stored according to a certain data model. It has a small degree of redundancy, high data independence and scalability, and can be shared with various users.

Database Data is permanently stored, organized, and shared.

 

Database Management System: Scientifically organizes and stores data, and obtains and maintains data from colleges and universities.

1. Data Definition

2. Data organization, storage and management

3. data manipulation

4. Database Transaction Management and Operation Management

5. database creation and maintenance functions

6. Other functions

 

Database Management Technology:1.Manual management2.File System3.Database System

 

Database System features:1.IDC2.High data sharing, low redundancy, and easy expansion3.High Data independence4.Data fromDBMSUnified management and control

 

Data Model category:1.Conceptual Model2.Logical and physical models

 

Composition of the data model:1.Data Structure2.Data Operations3.Integrity constraints

 

Data structure category:1.Which is related to the object type, content, and nature2.Objects related to data connections

 

Category of Data Operations: Query and update

 

Constraints on Data Integrity: in a relational model, any link must meet two conditions: entity integrity and reference integrity.

 

A representation of a conceptual model: entity-contact method (E-RFigure)

Solid shape: rectangle, property: elliptical, contact: Diamond.

 

The most basic specification of a relational model: each component of a link must be an inseparable data item, that is, tables are not allowed in the table.

 

The constraints on link integrity include entity integrity, referential integrity, and user-defined integrity.

 

Mode

Chapter 2 Relational Database

 

A domain is a set of values of the same data type.

 

Cartesian product is a set operation above the domain.

 

Candidate code: if the value of an attribute group in a link uniquely represents a ancestor, the attribute group is a candidate code.

 

Master code: a link has multiple candidate codes. select one of them as the master code.

 

The attributes of candidate codes are called as primary attributes.

 

Attributes that are not included in any candidate code are called non-primary or non-Code attributes.

 

Full code: all attributes of the link mode are candidate codes of the link mode.

 

There are three types of relationships: Basic relationships (also known as basic tables or base tables), query tables, and view charts.

A basic table is an actually existing table, which is the logical representation of the actually stored data.

The query table is the table corresponding to the query result.

A visual chart is a table exported from a basic table or other visual charts. It is a virtual table and does not correspond to the actually stored data.

 

In a relational database, the relational model is type and the Relational Value is value. The link mode is the description of the link.

 

Commonly used relational operations in a relational model include query operations, insert operations, delete operations, and modify operations.

 

Query operations can be divided into: selection, projection, join, division, sum, difference, intersection, and Cartesian product.

Where selection, projection, sum, difference, and Cartesian product are5.

 

Relational algebra, ancestor relational calculus, and domain relational calculus are fully equivalent in terms of expressive power.

 

Relational Data languages can be divided into three types:1.Relational algebra language2.Relational algorithm language3.A language that features relational algebra and relational calculus.

 

Three types of integrity constraints of a link: entity integrity, referential integrity, and user-defined integrity.

Entity integrity and reference integrity are the integrity constraints that must be met by the relational model. They are called the two immutability of relations and should be automatically supported by the relational system.

 

Entity Integrity: if an attribute (one or more attributes)AIs the basic relationshipRANULL values cannot be obtained.

 

Code

 

Integrity rules: Take null values or equalSThe primary code value of a tuples in.

 

Relational algebra uses four types of operators: Set operators, special Relational operators, and arithmetic comparison logical operators.

 

Relational Algorithm

 

 

Chapter 3 Standard relational database languageSQL

 

Mode

 

Index