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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‘;
#betweenselect
* 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_namealter 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_namealter 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testalter table position add(test char(10));
#表position 修改列testalter 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testalter 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; |