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
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);
#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;