一、主键、外键补充
create table tb1用户表(
id int not null auto_increment primary key,
name char(10),
department_id int,
p_id int,
constraint fk_1 foreign key (department_id,p_id) references tb2(tid,xid)
)engine=innodb default charset=utf8;
补充：主键
一个表只能有一个主键
主键可以由多列组成
补充：外键 ?
CREATE TABLE t5 (
nid int(11) NOT NULL AUTO_INCREMENT,
pid int(11) not NULL,
num int(11),
primary key(nid,pid)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
create table t6(
id int auto_increment primary key,
name char(10),
id1 int,
id2 int,
CONSTRAINT fk_t5_t6 foreign key (id1,id2) REFERENCES t1(nid,pid)
)engine=innodb default charset=utf8;
二、数据行
insert into tb1(name,age) values('alex',18);
insert into tb1(name,age) values('alex',18),('egon',19),('yuan',20); 可以同时插入多条数据
update tb1 set name='root' where id > 10
select * from tb;
select id,name from tb;
三、对于自增补充：
desc t10; 查看该表的创建方式：列名，是否可以为空，数据类型，是否为主键，是否为自增
show create table t10;
show create table t10 G;
alter table t10 AUTO_INCREMENT=20; 修改下次开始自增的值
MySQL: 自增步长
基于会话级别：
show session variables like 'auto_inc%'; 查看全局变量
set session auto_increment_increment=2; 设置会话步长
# set session auto_increment_offset=10;
基于全局级别：
show global variables like 'auto_inc%'; 查看全局变量
set global auto_increment_increment=2; 设置会话步长
# set global auto_increment_offset=10;
SqlServer：自增步长：
基于表级别：
CREATE TABLE `t5` (
`nid` int(11) NOT NULL AUTO_INCREMENT,
`pid` int(11) NOT NULL,
`num` int(11) DEFAULT NULL,
PRIMARY KEY (`nid`,`pid`)
) ENGINE=InnoDB AUTO_INCREMENT=4, 步长=2 DEFAULT CHARSET=utf8
CREATE TABLE `t6` (
`nid` int(11) NOT NULL AUTO_INCREMENT,
`pid` int(11) NOT NULL,
`num` int(11) DEFAULT NULL,
PRIMARY KEY (`nid`,`pid`)
) ENGINE=InnoDB AUTO_INCREMENT=4, 步长=20 DEFAULT CHARSET=utf8
四、 今日内容：
0. 唯一索引：约束该列中数据唯一
create table t1(
id int ....,
num int,
xx int,
unique 唯一索引名称 (列名,列名), 联合唯一
constraint ....
)
#
1 1 1
2 1 2
PS:
唯一索引：
约束不能重复（可以为空）
PS: 主键不能重复（不能为空）
加速查找
1. 外键的变种
a. 用户表和部门表
用户：
1 alex 1
2 root 1
3 egon 2
4 laoyao 3
部门:
1 服务
2 保安
3 公关
===》 一对多
b. 用户表和博客表
用户表：
1 alex
2 root
3 egon
4 laoyao
博客表：
FK() + 唯一
1 /yuanchenqi/ 4
2 /alex3714/ 1
3 /asdfasdf/ 3
4 /ffffffff/ 2
===> 一对一
create table userinfo1(
id int auto_increment primary key,
name char(10),
gender char(10),
email varchar(64)
)engine=innodb default charset=utf8;
create table admin(
id int not null auto_increment primary key,
username varchar(64) not null,
password VARCHAR(64) not null,
user_id int not null,
unique uq_u1 (user_id),
CONSTRAINT fk_admin_u1 FOREIGN key (user_id) REFERENCES userinfo1(id)
)engine=innodb default charset=utf8;
c. 用户表（百合网） 相亲记录表
示例1：
用户表
相亲表
示例2：
用户表
主机表
用户主机关系表
===》多对多
create table userinfo2(
id int auto_increment primary key,
name char(10),
gender char(10),
email varchar(64)
)engine=innodb default charset=utf8;
create table host(
id int auto_increment primary key,
hostname char(64)
)engine=innodb default charset=utf8;
create table user2host(
id int auto_increment primary key,
userid int not null,
hostid int not null,
unique uq_user_host (userid,hostid),
CONSTRAINT fk_u2h_user FOREIGN key (userid) REFERENCES userinfo2(id),
CONSTRAINT fk_u2h_host FOREIGN key (hostid) REFERENCES host(id)
)engine=innodb default charset=utf8;
2. SQL语句数据行操作补充
create table tb12(
id int auto_increment primary key,
name varchar(32),
age int
)engine=innodb default charset=utf8;
增
insert into tb11(name,age) values('alex',12);
insert into tb11(name,age) values('alex',12),('root',18);
insert into tb12(name,age) select name,age from tb11; 将tb11中的数据插入到tb12
删
delete from tb12;
delete from tb12 where id !=2
delete from tb12 where id =2
delete from tb12 where id > 2
delete from tb12 where id >=2
delete from tb12 where id >=2 or name='alex'
改
update tb12 set name='alex' where id>12 and name='xx'
update tb12 set name='alex',age=19 where id>12 and name='xx'
查（重点）
select * from tb12;
select id,name from tb12;
select id,name from tb12 where id > 10 or name ='xxx';
select id,name as cname from tb12 where id > 10 or name ='xxx';
select name,age,11 from tb12;
其他：
select * from tb12 where id != 1
select * from tb12 where id in (1,5,12);
select * from tb12 where id not in (1,5,12);
select * from tb12 where id in (select id from tb11)
select * from tb12 where id between 5 and 12;
通配符：
select * from tb12 where name like "a%"
select * from tb12 where name like "a_"
分页：
select * from tb12 limit 10; 查看该表前10行数据
select * from tb12 limit 0,10; 从1开始取10行数据
select * from tb12 limit 10,10; 从11开始取10行数据
select * from tb12 limit 20,10; 从21开始取10行数据
select * from tb12 limit 10 offset 20; 从第21行开始读取，读取10行；
结合Python分页：
# page = input('请输入要查看的页码')
# page = int(page)
# (page-1) * 10
# select * from tb12 limit 0,10; 1
# select * from tb12 limit 10,10;2
排序：
select * from tb12 order by id desc; 大到小
select * from tb12 order by id asc; 小到大
select * from tb12 order by age desc,id desc;
取后10条数据
select * from tb12 order by id desc limit 10;
分组：
select count(id),max(id),part_id from userinfo5 group by part_id;
聚合函数：
count
max
min
sum
avg
**** 如果对于聚合函数结果进行二次筛选时？必须使用having ****
select count(id),part_id from userinfo5 group by part_id having count(id) > 1;
select count(id),part_id from userinfo5 where id > 0 group by part_id having count(id) > 1;
连表操作：
select * from userinfo5,department5 where userinfo5.part_id = department5.id
select * from userinfo5 left join department5 on userinfo5.part_id = department5.id
select * from department5 left join userinfo5 on userinfo5.part_id = department5.id
# userinfo5左边全部显示
# select * from userinfo5 left join department5 on userinfo5.part_id = department5.id
# department5右边全部显示
# select * from userinfo5 right join department5 on userinfo5.part_id = department5.id
将出现null时一行隐藏
select * from userinfo5 innder join department5 on userinfo5.part_id = department5.id
将多个（3个）表连接起来：
select * from
department5
left join userinfo5 on userinfo5.part_id = department5.id
left join userinfo6 on userinfo5.part_id = department5.id
将多个（5个）表连接起来：
select
score.sid,
student.sid
from
score
left join student on score.student_id = student.sid
left join course on score.course_id = course.cid
left join class on student.class_id = class.cid
left join teacher on course.teacher_id=teacher.tid
select count(id) from userinfo5;
作业练习：
http://www.cnblogs.com/wupeiqi/articles/5729934.html
10-15个完成