database

I. Basic Concepts Database

1, the database DataBase, referred to as DB

2. The concept: What is a database? Storing data warehouse

3, the database features:

Persistent storage of data, the database is essentially a file system
Convenient data storage and management
The use of a unified database manipulation language -SQL language

4, common database management system (DataBase Management System: DBMS)

MySQL : the Oracle's free open-source database, small and medium, 6+ start charging
The Oracle : the Oracle's large database
DB2: IBM's large database
SQL Server: Microsoft's large database
SQLite: small mobile devices embedded database

Two. MySQL-related operations

2.1 Installation

See Fig.

2.2 Uninstall

1, completely remove the entire software in the control panel

2, delete the ProgramData directory of MySQL

2.3 Configuration

Startup and shutdown services
- start up
  - In the cmd window or enter services.msc in the operation of open systems and services, manually click to open
  - Enter net start mysql in cmd
- shut down
  - In cmd or type services.msc in the operation of open system service window, manually click Pause
  - Enter net stop mysql in cmd
Login: Type in cmd
- mysql -u -p password account
- mysql -u account -p, Enter, enter the password
- Password mysql -h target ip -uroot -p goals
drop out:
- exit
- quit
- Close the cmd window

III. Structure of the database

Database Project

Entity class table

Property fields

Object records

Four. SQL

The concept: SQL: Structured Query Language, Structured Query Language

Most relational data have the same SQL syntax, but there are a number of different database operation, this difference is called "dialects."

The general syntax:

1, SQL statement can be written in a single line or multiple lines, end with a semicolon

2, SQL keywords are not case sensitive, use uppercase generally recommended

3, SQL statements can be used in a number of spacing and indentation to improve readability

4, SQL syntax Three comments

a, single-line comment: - footnotes

b, single-line comment: # content annotation (MySQL dialect)

c, multi-line comments: / * comment * content /

Five. SQL classification

5.1 DDL Data Definition Language

For defining database objects: databases, tables, columns,

Keywords: create, alter, drop, etc.

5.2 DML Data Manipulation Language

For additions and deletions to the data table in the database

Keywords: insert, delete, update

5.3DQL data query language

For data query the database

关键字：select、on、where、order by、asc、desc、group by、limit、between and、and、or、in、like

5.4 DCL Data Control Language

For access and security levels defined in the database

Keywords: revoke, grant

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