MySQL 基础操作

· MySQL中不分大小写
· MySQL中分为DML(数据操作语言)  和 DDL(数据定义语音)

DML(数据操作语言):

SELECT - 从数据库表中获取数据

UPDATE - 更新数据库表中的数据

DELETE - 从数据库表中删除数据

INSERT INTO - 向数据库表中插入数据

DDL(数据定义语言):

CREATE DATABASE - 创建新数据库

ALTER DATABASE - 修改数据库

CREATE TABLE - 创建新表

ALTER TABLE - 变更（改变）数据库表

DROP TABLE - 删除表

CREATE INDEX - 创建索引（搜索键）

DROP INDEX - 删除索引

用例子记录

1.SELECT * FROM Customers

ORDER BY Country ASC, CustomerName DESC; (order by 不需要and/or)

2.INSERT (...) VALUES (...);

INSERT INTO Customers (CustomerName, ContactName, Address, City, PostalCode, Country) VALUES ('Cardinal', 'Tom B. Erichsen', 'Skagen 21', 'Stavanger', '4006', 'Norway');

3.NULL(总是用is)

SELECT * FROM CUSTOMERS WHERE ADDRESS IS NOT NULL

4.UPDATE(TABLE_NAME)

SET(ContactName = 'Alfred Schmidt', City = Frankfurt'),

WHERE CustomerID = 1;

5.DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste';

6.Select TOP 3 * FROM Customers

WHERE Country = 'Germany';

或者

Select * FROM Customers

WHERE Country = 'Germany'

LIMIT 3;

7.Select TOP 50 PERCENT * FROM Customers

8.SELECT MAX(Price)

FROM table_name

WHERE condition;

9.(INNER) JOIN: Returns records that have matching values in both tables

LEFT (OUTER) JOIN: Returns all records from the left table, and the matched records from the right table

RIGHT (OUTER) JOIN: Returns all records from the right table, and the matched records from the left table

FULL (OUTER) JOIN: Returns all records when there is a match in either left or right table

例子看这个

https://www.cnblogs.com/lijingran/p/9001302.html

select * from A  //以A为准

left join B

on A.aID = B.bID

---

select * from A //以B为准

right join B 

on A.aID = B.bID

---

select * from A // 两个都是

innerjoin B

on A.aID = B.bID