MySQL语法大全_自己整理的学习笔记

select * from emp;  #注释

#---------------------------

#----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
#---------------------------

#----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);
#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;