MySQL-----表操作

select查询

1 简单查询
select * from employee;
select name,salary from employee;

2 where条件
select name,salary from employee where salary > 10000;
select name,salary from employee where salary > 10000 and salary < 20000;
select name,salary from employee where salary between 10000 and 20000;
select name,salary from employee where salary not between 10000 and 20000;

select name,salary from employee where salary = 10000 or salary = 20000 or salary = 30000;
select name,salary from employee where salary in (10000,20000,30000);


select * from employee where salary = 10000 or age = 18 or sex='male';

select * from employee where post_comment is Null;
select * from employee where post_comment = Null;
select * from employee where post_comment is not Null;

 select * from employee where name like '%n%';

select * from employee where name like 'e__n';

3 group by分组
mysql> select depart_id,group_concat(name)  from employee group by depart_id;
+-----------+--------------------------------------------------------------+
| depart_id | group_concat(name)                                           |
+-----------+--------------------------------------------------------------+
|         1 | egon,alex,wupeiqi,yuanhao,liwenzhou,jingliyang,jinxin,成龙   |
|         2 | 歪歪,丫丫,丁丁,星星,格格                                     |
|         3 | 张野,程咬金,程咬银,程咬铜,程咬铁                             |
+-----------+--------------------------------------------------------------+
3 rows in set (0.00 sec)

mysql> select depart_id,count(id)  from employee group by depart_id;
+-----------+-----------+
| depart_id | count(id) |
+-----------+-----------+
|         1 |         8 |
|         2 |         5 |
|         3 |         5 |
+-----------+-----------+
3 rows in set (0.01 sec)

mysql> select depart_id,group_concat(id)  from employee group by depart_id;
+-----------+------------------+
| depart_id | group_concat(id) |
+-----------+------------------+
|         1 | 1,2,3,4,5,6,7,8  |
|         2 | 9,10,11,12,13    |
|         3 | 14,15,16,17,18   |
+-----------+------------------+
3 rows in set (0.00 sec)

mysql> select depart_id,count(id)  from employee group by depart_id;
+-----------+-----------+
| depart_id | count(id) |
+-----------+-----------+
|         1 |         8 |
|         2 |         5 |
|         3 |         5 |
+-----------+-----------+
3 rows in set (0.00 sec)

mysql> select depart_id,max(salary) from employee group by depart_id;
+-----------+-------------+
| depart_id | max(salary) |
+-----------+-------------+
|         1 |  1000000.31 |
|         2 |     4000.33 |
|         3 |    20000.00 |
+-----------+-------------+
3 rows in set (0.00 sec)

mysql> select depart_id,min(salary) from employee group by depart_id;
+-----------+-------------+
| depart_id | min(salary) |
+-----------+-------------+
|         1 |     2100.00 |
|         2 |     1000.37 |
|         3 |    10000.13 |
+-----------+-------------+
3 rows in set (0.00 sec)

mysql> select depart_id,sum(salary) from employee group by depart_id;
+-----------+-------------+
| depart_id | sum(salary) |
+-----------+-------------+
|         1 |  1070200.64 |
|         2 |    13001.47 |
|         3 |    84000.13 |
+-----------+-------------+
3 rows in set (0.00 sec)

mysql> select depart_id,avg(salary) from employee group by depart_id;
+-----------+---------------+
| depart_id | avg(salary)   |
+-----------+---------------+
|         1 | 133775.080000 |
|         2 |   2600.294000 |
|         3 |  16800.026000 |
+-----------+---------------+
3 rows in set (0.00 sec)

建立表之间的关系

创建表
语法：
create table 表名(
字段名1 类型[(宽度) 约束条件],
字段名2 类型[(宽度) 约束条件],
字段名3 类型[(宽度) 约束条件]
);
注意：
1. 在同一张表中，字段名是不能相同
2. 宽度和约束条件可选
3. 字段名和类型是必须的

永久解决编码问题
#1. 修改配置文件
[mysqld]
default-character-set=utf8
[client]
default-character-set=utf8
[mysql]
default-character-set=utf8

#mysql5.5以上：修改方式有所改动
    [mysqld]
    character-set-server=utf8
    collation-server=utf8_general_ci
    [client]
    default-character-set=utf8
    [mysql]
    default-character-set=utf8

#2. 重启服务
#3. 查看修改结果：
s
show variables like '%char%'
注意注意注意：表中的最后一个字段不要加逗号




1 多对一：左边表的多条记录对应右面表的唯一一条记录
create table dep(
id int primary key auto_increment, #被关联的字段必须保证是唯一的
name varchar(20),
comment varchar(50)
);


create table emp(
id int primary key auto_increment,
name varchar(20),
dep_id int, #关联的字段，一定要保证是可以重复的
constraint fk_depid_id foreign key(dep_id)  references dep(id)
on update cascade
on delete cascade
);

建立多对一的关系需要注意
1 先建立被关联的表，被关联的字段必须保证是唯一的
2 再创建关联的表，关联的字段，一定要保证是可以重复的
ps：关联的字段一定是来自于表关联的表对应字段的值


2 一对一的关系：
create table user(
uid int primary key auto_increment,
name varchar(15)
);
insert into user(name) values
('egon1'),
('egon2'),
('egon3'),
('egon4'),
('egon5'),
('egon6');



create table admin(
id int primary key auto_increment,
user_id int unique,
password varchar(20),
foreign key(user_id) references user(uid)
on update cascade
on delete cascade
);


insert into admin(user_id,password) values
(3,'alex3714'),
(5,'alex371asdf4');

乱乱的练习

create table class(
cid int primary key auto_increment,
caption varchar(20)
);

create table student(
sid int primary key auto_increment,
sname varchar(20),
gender varchar(20),
class_id int,
foreign key(class_id) references class(cid)
on delete cascade
on update cascade
)engine=innodb;

create table teacher(
tid int primary key auto_increment,
tname varchar(20)
);

create table course(
cid int primary key auto_increment,
cname varchar(10),
teacher_id int,
foreign key(teacher_id) references teacher(tid)
on delete cascade
on update cascade
)engine=innodb;

create table score(
sid int primary key auto_increment,
student_id int not null,
corse_id int not null,
number int
);
insert into class(caption) values('三年二班'),('一年三班'),('三年一班');
insert into student(sname,gender,class_id) values('钢蛋','女',1),
('铁锤','女',1),
('山炮','男',2);
insert into teacher(tname) values('刘老师'),('田老师'),('林老师');
insert into course(cname,teacher_id) values('生物',1),('体育',1),('物理',2);
insert into score values(1,1,1,60),(2,1,2,59),(3,2,2,100);





练习：账号信息表，用户组，主机表，主机组


复制代码
#用户表
create table user(
id int not null unique auto_increment,
username varchar(20) not null,
password varchar(50) not null,
primary key(username,password)
);

insert into user(username,password) values
('root','123'),
('egon','456'),
('alex','alex3714')
;


#用户组表
create table usergroup(
id int primary key auto_increment,
groupname varchar(20) not null unique
);

insert into usergroup(groupname) values
('IT'),
('Sale'),
('Finance'),
('boss')
;


#主机表
create table host(
id int primary key auto_increment,
ip char(15) not null unique default '127.0.0.1'
);

insert into host(ip) values
('172.16.45.2'),
('172.16.31.10'),
('172.16.45.3'),
('172.16.31.11'),
('172.10.45.3'),
('172.10.45.4'),
('172.10.45.5'),
('192.168.1.20'),
('192.168.1.21'),
('192.168.1.22'),
('192.168.2.23'),
('192.168.2.223'),
('192.168.2.24'),
('192.168.3.22'),
('192.168.3.23'),
('192.168.3.24')
;


#业务线表
create table business(
id int primary key auto_increment,
business varchar(20) not null unique
);
insert into business(business) values
('轻松贷'),
('随便花'),
('大富翁'),
('穷一生')
;


#建关系：user与usergroup

create table user2usergroup(
id int not null unique auto_increment,
user_id int not null,
group_id int not null,
primary key(user_id,group_id),
foreign key(user_id) references user(id),
foreign key(group_id) references usergroup(id)
);

insert into user2usergroup(user_id,group_id) values
(1,1),
(1,2),
(1,3),
(1,4),
(2,3),
(2,4),
(3,4)
;



#建关系：host与business

create table host2business(
id int not null unique auto_increment,
host_id int not null,
business_id int not null,
primary key(host_id,business_id),
foreign key(host_id) references host(id),
foreign key(business_id) references business(id)
);

insert into host2business(host_id,business_id) values
(1,1),
(1,2),
(1,3),
(2,2),
(2,3),
(3,4)
;

#建关系：user与host

create table user2host(
id int not null unique auto_increment,
user_id int not null,
host_id int not null,
primary key(user_id,host_id),
foreign key(user_id) references user(id),
foreign key(host_id) references host(id)
);

insert into user2host(user_id,host_id) values
(1,1),
(1,2),
(1,3),
(1,4),
(1,5),
(1,6),
(1,7),
(1,8),
(1,9),
(1,10),
(1,11),
(1,12),
(1,13),
(1,14),
(1,15),
(1,16),
(2,2),
(2,3),
(2,4),
(2,5),
(3,10),
(3,11),
(3,12)












employee 表
create table employee(
id int not null unique auto_increment,
name varchar(20) not null,
sex enum('male','female') not null default 'male', #大部分是男的
age int(3) unsigned not null default 28,
hire_date date not null,
post varchar(50),
post_comment varchar(100),
salary double(15,2),
office int, #一个部门一个屋子
depart_id int
);

insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values
('egon','male',18,'20170301','老男孩驻沙河办事处外交大使',7300.33,401,1), #以下是教学部
('alex','male',78,'20150302','teacher',1000000.31,401,1),
('wupeiqi','male',81,'20130305','teacher',8300,401,1),
('yuanhao','male',73,'20140701','teacher',3500,401,1),
('liwenzhou','male',28,'20121101','teacher',2100,401,1),
('jingliyang','female',18,'20110211','teacher',9000,401,1),
('jinxin','male',18,'19000301','teacher',30000,401,1),
('成龙','male',48,'20101111','teacher',10000,401,1),

('歪歪','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门
('丫丫','female',38,'20101101','sale',2000.35,402,2),
('丁丁','female',18,'20110312','sale',1000.37,402,2),
('星星','female',18,'20160513','sale',3000.29,402,2),
('格格','female',28,'20170127','sale',4000.33,402,2),

('张野','male',28,'20160311','operation',10000.13,403,3), #以下是运营部门
('程咬金','male',18,'19970312','operation',20000,403,3),
('程咬银','female',18,'20130311','operation',19000,403,3),
('程咬铜','male',18,'20150411','operation',18000,403,3),
('程咬铁','female',18,'20140512','operation',17000,403,3)
;