SQL language

1. SQL brief introduction

1.SQL  english ：Structured Query Language, abbreviation SQL
2. Structured query language , A programming language for operating relational databases 
3. Define a unified standard for operating all relational databases 
4. For unified requests , There may be some differences in the operation mode of each database ,
 We call it “ dialect ”.

2. SQL General grammar

1.SQL Statements can be written in one or more lines , It ends with a semicolon .
2.MySQL Database SQL Statement is case insensitive , It is recommended to use uppercase .
3. notes   
     *  Single-line comments ：--  The comment   or  # The comment （MySQL specific ）
     *  Multiline comment ：/*  notes  */

3. SQL classification

• DDL（Data Definition Langage） Data definition language , Used to define database objects ： database , surface , Column, etc.
• DML（Data Manipulation Langage） Database operation language , It is used to add, delete and modify the bid winning data in the database
• DQL（Data Query Langage） Data query language , Used to query the records of tables in the database （ data ）
• DCL（Data Control Langage） Data control language , It is used to define the access rights and security level of the database , And create users
  

4. DDL

1.DDL Operating the database

Open Command Prompt


2.DDL Operation table




SQL What are the data types of ？

Make a case

5. Graphic tool Navicat

Navicat 
* Navicat Premium12  It's management and development MySQL or MariaDB The ideal solution .
*  This comprehensive front-end tool for database management 、 Development and maintenance provides an intuitive and powerful graphical interface 
*  Official website  http://www.navicat.com.cn
 tips：[ This is the cracked version taught in detail by a blogger ](https://www.cnblogs.com/xibb/p/11975811.html)

First time tutorial ：


Select the database you want to operate , Click query to write SQL Statement to operate on the database , Code execution , Select the code you want to execute , Right click to select execute the selected .

6. DML

1. Add data

2. Modifying data

3. Delete data

7. DQL

1. The query syntax

2. Basic query
tips：* The number represents all Try not to use , Because I don't know the list you want to operate

3. Conditions of the query

4. Sort query

5. Aggregate functions

6. Group query


7. Paging query