今天完成的内容：通过w3cschool学习了mysql,准备为了任务1做准备

创建数据表，并插入数据

create table persons(

  id int,

 lastname varchar(20),

 firstname varchar(20),

 address varchar(20),

 city varchar(20)

)

insert into persons values ('1','adams','joho','oxford street','london');

insert into persons values ('2','bush','george','fifth avenue','new york');

insert into persons values ('3','carter','thomas','changan street','beijing');

insert into persons values ('5','carter','thomas','changan street','beijing');

  表外添加约束：

#表外添加约束

alter table persons 

add CONSTRAINT primary key (id);

 去重复：

select DISTINCT

lastname from

 persons;

 where子句:

select * from

persons 

where city='beijing';

select *from persons

where address='fifth avenue';

#and(且)

select *from persons 

where lastname='carter' 

and firstname='thomas';

#OR（或）

select *from persons 

WHERE firstname='thomas'

or lastname='carter';

#使用and和or显示名thomas姓为caeter

SELECT * FROM Persons 

WHERE (FirstName='Thomas' OR FirstName='William')

AND LastName='Carter'

  表2

create table orders(

  company varchar(20),

  ordernumber int

)

insert into orders values('ibm','3532');

insert into orders values('w3school','2356');

insert into orders values('apple','4698');

insert into orders values('w3school','6953');

 order by语句

select 

company,ordernumber

from orders order by company;

select

company,ordernumber 

from 

orders 

order by company ,ordernumber;

Desc降序和asc升序

select company,ordernumber

from orders 

order BY company

DESC;

select company,ordernumber

from orders

ORDER BY company

DESC,ordernumber 

ASC;

  insert into语句

#插入数值

insert into persons values ('4','carter','thomas','changan street','beijing');

select * from persons;

select 

*from persons

where id=4;

#在指定的列中插入数据

insert into persons (lastname,address) VALUES ('wilson','champs-elysees');

select * from persons;

  update修改

#改

update persons SET firstname ='fred' WHERE lastname ='wilson';

#修改为zhongshan23 并且city地址添加nanjing(思路：根据lastname下whilson来修改)

update persons SET address = 'Zhongshan 23', city ='nanjing' WHERE lastname='wilson';

  delete删除

#删除

select * from persons;

delete from persons where lastName ='wilson';

delete from abc

    明天计划：准备尝试做任务1关于mysql部分。

    今天遇到的问题：1、英语不好，有一些关键字记不住  ——解决方法：百度

    收获：学会了一些基本的sql语句。