Shulou(Shulou.com)06/03 Report--

Introduction to the basics of MySQL database this outline:

A brief introduction to mainstream databases

General classification of database

MySQL database management

First, a brief introduction to mainstream databases

SQL Server (Microsoft products)-- mainly for clients, with very little concurrency

Oriented to Windows operating system

Simple and easy to use

Oracle (Oracle products)

Oriented to Windows operating system

Simple and easy to use

DB2 (IBM products)

For all mainstream platforms

Large, safe and perfect

MySQL (acquired by Oracle)

Free, open source, small size and general classification of databases are mainly divided into relational databases and non-relational databases

​ relational database system is a database system based on relational model, and its basic concept comes from relational model.

The ​ relational model is based on the theory of relational algebra. The data structure uses a two-dimensional data table that is easy to understand and can be expressed directly by a simple "entity relation" (Emer R) diagram.

The ​ Emurr diagram contains three elements: entities (data objects), relationships and attributes.

Main application examples

Non-relational database

​ non-relational database, also known as NoSQL (Not Only SQL), stores data without a relational model and does not require a fixed table format.

As a supplement to relational database, ​ non-relational database plays an important role in high efficiency and high performance in the increasingly rapid development of the website era.

​ is not based on the relational model, but on the Kmuri V relationship (key- key; value- value)

​ value can also be a specific object (including: attributes, behaviors)

3. MySQL database management 1. Basic management operations

View database list information

​ show databases

View all data table information in a database

​ show tables

Display data table structure information

​ describe [database name]. Table name

2. SQL language

Overview

SQL is the abbreviation of Structured Query Language, that is, structured query language.

A standard language belonging to relational database

Used to maintain and manage databases, such as data query, data update, access control, object management, etc.

classification

DDL: data definition language

DML: data manipulation language

DQL: data query language

DCL: data control language

Specific explanation

DDL statement

​ is mainly used to create database objects, such as libraries, tables, indexes, etc.

Create database: create database database name; example: create database test; create data table: create table table name (field definition); example: create table users (name char (4) not null,passwd int (10) not null,primary key (name)); delete database: drop database database name; example: drop database test; delete data table: drop table [database name]. Table name; example: drop table test.user; & use test; drop table user

DML statement

​ is mainly used to manage the data in the table, including the following operations:

​ INSERT: inserting new data

​ UPDATE: update existing data

​ DELETE: delete unwanted data

Insert a new data record: insert into table name (field 1, field 2.) Values (value of field 1, value of field 2.); example: insert into user (name,passwd) values ('zfm',123456); update original data: update table name set field 1 = value 1 [, field name 2 = value 2] where conditional filtering; example: update user set passwd=123 where name='zfmdd'; deletes the specified data record: delete from table name where conditional expression (all records in the table will be deleted without where) instance: delete from test where name='zfmdd'

DQL statement

​ data query statement, mainly used to find qualified data records in the data table

No condition can be specified when querying: SELECT field name 1, field name 2 FROM table name WHERE conditional expression; example: select * from test where name='zfmdd'; view the first few rows of data: Select * from table limit rows

DCL statement

​ is mainly used to manage object permissions in the system.

Set user permissions: grant permission list on database name. Table name to user name @ source address [identified by 'password]; example: grant replication test.slave on *. * to' myslave'@'192.168.142.135' identified by 'asd123'; view user rights: show grants for user name @ source address; example: show grants for' myslave'@'192.168.142.135'; revoke user rights: revoke permission list on database name. Table name from user name @ source address; example: revoke replication on test.slave from 'myslave'@'192.168.142.135'

Alternative type

Change the specific field definition in a specific data table: alter table table name modify column field name new definition; add field alter table table name add new field name type (define length) [comment 'comment content to be added']; add keywords "first", "after field name (after a field)" delete field alter table table name drop field name after the type

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.