[Mysql ] mysql基础笔记

╰+哭是因爲堅強的太久メ 2023-10-04 14:16 11阅读 0赞

\#----命令行连接MySql---------

\#启动mysql服务器  
net start mysql

\#关闭  
net stop mysql

\#进入  
mysql -h 主机地址 -u 用户名 －p 用户密码

\#退出  
exit

status;  
显示当前mysql的version的各种信息。

\#---------------------------  
\#----MySql用户管理---------

\#修改密码:首先在DOS 下进入mysql安装路径的bin目录下，然后键入以下命令:  
mysqladmin -uroot -p123 password 456;

\#增加用户  
\#格式:grant 权限 on 数据库.\* to 用户名@登录主机 identified by ‘密码’  
/\*  
如，增加一个用户user1密码为password1，让其可以在本机上登录， 并对所有数据库有查询、插入、修改、删除的权限。首先用以root用户连入mysql，然后键入以下命令：  
grant select,insert,update,delete on *.* to user1@localhost Identified by “password1”;  
如果希望该用户能够在任何机器上登陆mysql，则将localhost改为"%"。  
如果你不想user1有密码，可以再打一个命令将密码去掉。  
grant select,insert,update,delete on mydb.\* to user1@localhost identified by “”;  
\*/

grant all privileges on wpj1105.\* to sunxiao@localhost identified by ‘123’; \#all privileges 所有权限

\#----------------------------  
\#-----MySql数据库操作基础-----

\#显示数据库  
show databases;

\#判断是否存在数据库wpj1105,有的话先删除  
drop database if exists wpj1105;

\#创建数据库  
create database wpj1105;

\#删除数据库  
drop database wpj1105;

\#使用该数据库  
use wpj1105;

\#显示数据库中的表  
show tables;

\#先判断表是否存在,存在先删除  
drop table if exists student;

\#创建表  
create table student(  
id int auto\_increment primary key,  
name varchar(50),  
sex varchar(20),  
date varchar(50),  
content varchar(100)  
)default charset=utf8;

\#删除表  
drop table student;

\#查看表的结构  
describe student; \#可以简写为desc student;

\#插入数据  
insert into student values(null,‘aa’,‘男’,‘1988-10-2’,’…’);  
insert into student values(null,‘bb’,‘女’,‘1889-03-6’,’…’);  
insert into student values(null,‘cc’,‘男’,‘1889-08-8’,’…’);  
insert into student values(null,‘dd’,‘女’,‘1889-12-8’,’…’);  
insert into student values(null,‘ee’,‘女’,‘1889-09-6’,’…’);  
insert into student values(null,‘ff’,‘null’,‘1889-09-6’,’…’);  
\#查询表中的数据  
select \* from student;  
select id,name from student;

\#修改某一条数据  
update student set sex=‘男’ where id=4;

\#删除数据  
delete from student where id=5;

## and 且 ##

select \* from student where date>‘1988-1-2’ and date<‘1988-12-1’;

## or 或 ##

select \* from student where date<‘1988-11-2’ or date>‘1988-12-1’;

\#between  
select \* from student where date between ‘1988-1-2’ and ‘1988-12-1’;

\#in 查询制定集合内的数据  
select \* from student where id in (1,3,5);

\#排序 asc 升序 desc 降序  
select \* from student order by id asc;

\#分组查询 \#聚合函数  
select max(id),name,sex from student group by sex;

select min(date) from student;

select avg(id) as ‘求平均’ from student;

select count(\*) from student; \#统计表中总数

select count(sex) from student; \#统计表中性别总数 若有一条数据中sex为空的话,就不予以统计~

select sum(id) from student;

\#查询第i条以后到第j条的数据(不包括第i条)  
select \* from student limit 2,5; \#显示3-5条数据

\#巩固练习  
create table c(  
id int primary key auto\_increment,  
name varchar(10) not null,  
sex varchar(50) , \#DEFAULT ‘男’ ,  
age int unsigned, \#不能为负值(如为负值 则默认为0)  
sno int unique \#不可重复  
);

drop table c;  
desc c;

insert into c (id,name,sex,age,sno) values (null,‘涛哥’,‘男’,68,1);  
insert into c (id,name,sex,age,sno) values (null,‘aa’,‘男’,68,2);  
insert into c (id,name,sex,age,sno) values (null,‘平平’,‘男’,35,3);  
…

select \* from c;

\#修改数据  
update c set age=66 where id=2;  
update c set name=‘花花’,age=21,sex=‘女’ where id=2  
delete from c where age=21;

\#常用查询语句  
select name,age ,id from c  
select \* from c where age>40 and age<60; \#and  
select \* from c where age<40 or age<60; \#or  
select \* from c where age between 40 and 60 \#between  
select \* from c where age in (30,48,68,99); \#in 查询指定集合内的数据  
select \* from c order by age desc; \#order by （asc升序 des降序）

\#分组查询  
select name,max(age) from c group by sex; \#按性别分组查年龄最大值  
\#聚合函数  
select min(age) from c;  
select avg(age) as '平均年龄 ’ from c;  
select count(\*) from c; \#统计表中数据总数  
select sum(age) from c;

\#修改表的名字  
\#格式:alter table tbl\_name rename to new\_name  
alter table c rename to a;

\#表结构修改  
create table test  
(  
id int not null auto\_increment primary key, \#设定主键  
name varchar(20) not null default ‘NoName’, \#设定默认值  
department\_id int not null,  
position\_id int not null,  
unique (department\_id,position\_id) \#设定唯一值  
);

\#修改表的名字  
\#格式:alter table tbl\_name rename to new\_name  
alter table test rename to test\_rename;

\#向表中增加一个字段(列)  
\#格式:alter table tablename add columnname type;/alter table tablename add(columnname type);  
alter table test add columnname varchar(20);

\#修改表中某个字段的名字  
alter table tablename change columnname newcolumnname type; \#修改一个表的字段名  
alter table test change name uname varchar(50);

select \* from test;

\#表position 增加列test  
alter table position add(test char(10));  
\#表position 修改列test  
alter table position modify test char(20) not null;  
\#表position 修改列test 默认值  
alter table position alter test set default ‘system’;  
\#表position 去掉test 默认值  
alter table position alter test drop default;  
\#表position 去掉列test  
alter table position drop column test;  
\#表depart\_pos 删除主键  
alter table depart\_pos drop primary key;  
\#表depart\_pos 增加主键  
alter table depart\_pos add primary key PK\_depart\_pos  
(department\_id,position\_id);

\#(在桌面创建一个.txt结尾的文本文档，然后对应数据库的属性输入相对应的值，)再用文本方式将数据装入数据库表中（例如D:/mysql.txt）  
load data local infile “D:/mysql.txt” into table MYTABLE;

\#导入.sql文件命令（例如D:/mysql.sql）  
source d:/mysql.sql; \#或者 /. d:/mysql.sql;