Java学习路线-42：SQL进阶：约束、关系、连接

-- 查询部门编号为30的所有员工
select * from emp where deptno=30;
-- 查询所有销售员的姓名、编号和部门编号
select ename, empno, deptno from emp where job='销售员'
-- 查询奖金高于工资的员工
select * from emp where comm > sal;
-- 查询奖金高于工资60%的员工
select * from emp where comm > sal * 0.6;
-- 查询部门编号为10中所有经理，和部门编号编号为20中所有销售员的详细资料
select * from emp 
where (deptno=10 and job='经理')
or (deptno=20 and job='销售员');
-- 查询部门编号为10中所有经理，和部门编号编号为20中所有销售员，
-- 还有既不是经理又不是销售员但工资大于等于20000的所有员工详细资料
select * from emp 
where (deptno=10 and job='经理')
or (deptno=20 and job='销售员')
or (job not in ('经理', '销售员') and sal >= 2000);
-- 无奖金或奖金低于1000的员工
select * from emp where comm is null or comm < 1000;
-- 查询名字由3个字组成的员工(3个下划线)
select * from emp where ename like '___';
-- 查询2000年入职的员工
select * from emp where hiredate like '2000-%';
-- 查询所有员工，用编号升序排序
select * from emp order by empno asc;
-- 查询所有员工详细信息，用工资降序排序，如果工资相同使用入职日期升序排序
select * from emp order by sal desc, hiredate asc;
-- 查询每个部门的平均工资
select deptno, avg(sal) from emp group by deptno;
-- 查询每个部门雇员数量
select deptno, count(*) from emp group by deptno;
-- 查询每种工作的最高工资，最低工资，人数
select job, max(sal), min(sal), count(*) from emp group by job;

-- 查看MySQL的数据库编码
show variables like 'char%';
-- 临时设置变量
set character_set_client=utf8
set character_set_results=utf8

$ mysqldump -u用户名 -p密码 数据库名 > 要生成的SQL脚本路径

$ mysql -u用户名 -p密码 数据库名 < 要生成的SQL脚本路径
# 或者
> source 要生成的SQL脚本路径

-- 1、创建表时指定主键
create table stu(
    id int primary key,
    name varchar(20)
)
-- 或者
create table stu(
    id int,
    name varchar(20),
    primary key(id)
)
-- 2、已存在表添加主键
alter table stu add primary key(id);
-- 3、删除主键
alter table stu drop primary key;

create table stu(
    id int primary key auto_increment,
    name varchar(20)
)
-- 设置字段自增长
alter table stu change id id int auto_increment;
-- 删除自增长
alter table stu change id id int;

非空约束：不能为null
not null
唯一约束:不能重复
unique
create table stu(
    id int primary key auto_increment,
    name varchar(20) not null unique 
)

// 一对一关系 丈夫-妻子
class  Husband{
    private Wife wife;
}
class Wife{
    private Husband husband;
}
// 一对多关系 部门-员工
class Employee{
    private Department department;
}
class Department{
    private List<Employee> employee;
}
// 多对多关系 老师-学生
class Student{
    private List<Teacher> teachers
}
class Teacher{
    private List<Student> students
}

create table dept(
    deptno int primary key auto_increment,
    dname varchar(50)
)
insert into dept values(10, '人力部');
insert into dept values(20, '研发部');
insert into dept values(30, '财务部');
-- 创建表时添加外键约束
create table emp(
    empno int primary key auto_increment,
    ename varchar(50),
    dno int,
    constraint fk_emp_dept foreign key(dno) references dept(deptno)
)
-- 添加外键约束
alter table emp add constraint fk_emp_dept foreign key(dno) references dept(deptno)
insert into emp(ename) values('张三');
insert into emp(ename, dno) values('李四', 10);
insert into emp(ename, dno) values('王五', 20);

create table husband(
    hid int primary key auto_increment,
    hname varchar(50)
)
insert into husband(hname) values ('刘备'), ('关羽'), ('张飞')
create table wife(
    wid int primary key auto_increment,
    wname varchar(50),
    constraint fk_wife_husband foreign key(wid) references husband(hid)
)
-- wid 非空，唯一，引用hid
insert into wife(wid, wname) values(1, '杨贵妃');
insert into wife(wid, wname) values(2, '西施');

create table student(
    sid int primary key auto_increment,
    sname varchar(50)
)
create table teacher(
    tid int primary key auto_increment,
    tname varchar(50)
)
create table stu_tea(
    sid int,
    tid int,
    constraint fk_student foreign key(sid) references student(sid),
    constraint fk_teacher foreign key(tid) references teacher(tid)
)
insert into student(sname) values('段誉');
insert into student(sname) values('乔峰');
insert into student(sname) values('虚竹');
insert into teacher(tname) values('黄老师');
insert into teacher(tname) values('刘老师');
insert into teacher(tname) values('李老师');
insert into stu_tea(sid, tid) values(1, 1);
insert into stu_tea(sid, tid) values(2, 1);
insert into stu_tea(sid, tid) values(3, 1);
insert into stu_tea(sid, tid) values(1, 2);
insert into stu_tea(sid, tid) values(3, 2);
insert into stu_tea(sid, tid) values(1, 3);
insert into stu_tea(sid, tid) values(2, 3);

create table tb_a(id int, a_name varchar(50));
insert into tb_a(id, a_name) values(1, '1');
insert into tb_a(id, a_name) values(2, '2');
insert into tb_a(id, a_name) values(3, '3');
create table tb_b(id int, b_name varchar(50));
insert into tb_b(id, b_name) values(3, '3');
insert into tb_b(id, b_name) values(4, '4');
insert into tb_b(id, b_name) values(5, '5');
-- 不合并重复行
select * from tb_a union all select * from tb_b;
-- 合并重复行
select * from tb_a union select * from tb_b;

-- 方言
select * from 表1 别名1, 表2 别名2 where 别名1.xx = 别名2.xx;
-- 标准 (推荐)
select * from 表1 别名1 inner join 表2 别名2 on 别名1.xx = 别名2.xx;
-- 自然
select * from 表1 别名1 natural join 表2 别名2

(a, b, c) X (1, 2)
-> 
a1, a2, b1, b2, c1, c2

-- 笛卡尔积
select * from emp, dept
-- 员工对应部门信息
select * from emp, dept where emp.dno=dept.deptno;
-- 打印所有员工的姓名，部门名称, 取别名
select e.ename, d.dname
from emp e, dept d
where e.dno=d.deptno;

-- 标准推荐
select * from emp inner join dept on emp.dno=dept.deptno;
-- 自动加where条件
select * from emp natural join dept

-- 左外连接, 左表为主
select e.ename, ifnull(d.dname, '无部门') as dname
from emp e left outer join dept d
on e.dno=d.deptno;
-- 右外连接, 右表为主
select e.ename, d.dname
from emp e right outer join dept d
on e.dno=d.deptno;
-- 全外连接
select e.ename, d.dname
from emp e left outer join dept d
on e.dno=d.deptno;
union
select e.ename, d.dname
from emp e right outer join dept d
on e.dno=d.deptno;

-- 查询本公司工资最高的员工详细信息
select * from emp where sal=(select max(sal) from emp);

from 后作为表存在(多行多列)
where 后作为条件存在

-- 单行单列 
select * from 表1 别名1 where 列1[=, >, <, >=, <=, !=]
(select 列 from 表2 别名2 where 条件)
-- 多行单列
select * from 表1 别名1 where 列1[in, all, any]
(select 列 from 表2 别名2 where 条件)
-- 单行多列（一个对象）
select * from 表1 别名1 where (列1, 列2) in
(select 列1, 列2 from 表2 别名2 where 条件)
-- 多行多列
select * from 表1 别名1, 
(select ...) 别名2 where 条件

-- 工资高于平均工资的员工
select * from emp where sal > (select avg(sal) from emp);
-- 大于30部门所有人的工资的员工
select * from emp where sal > all(select sal from emp where deptno=30);
-- 和李白岗位部门都相同的员工
select * from emp where (job, deptno) in (select jobm, deptno from emp where ename ='李白');

-- 部门编号，部门名称，部门位置
select * from dept;
-- 部门人数
select deptno, count(*) from emp group by deptno
-- 整合
select d.* e1.cnt from dept d inner join 
(select deptno, count(*) cnt from emp group by deptno) as e1
on d.deptno=e1.deptno

select e.ename, m.ename
from emp e left outer join emp m
on e.mgr=m.empno;

-- 1、先查询员工
select e.empno, e.ename, e.deptno
from emp e, emp m
where e.mgr=m.empno and e.hiredate<m.hiredate
-- 2、查询部门名称
select e.empno, e.ename, d.dname
from emp e, emp m, dept d
where e.mgr=m.empno 
and e.hiredate<m.hiredate 
and e.deptno=d.deptno

select *
from emp e right outer join dept d
on e.deptno=d.deptno;

select job, count(*)
from emp e
group by job
having min(sal) > 15000

select ename
from emp e
where e.deptno = (select deptno from dept where dname='销售部')

-- 薪金高于公司平均薪金的所有员工信息
select * from emp where e.sal>(select avg(sal) from emp)
select e.*, d.dname, m.ename, s.grade 
from 
    emp e left outer join dept d on e.deptno=d.deptno
          left outer join emp m on e.mgr=m.empno
          left outer join salgrade s on e.sal between s.losal and s.hisal
where e.sal>(select avg(sal) from emp)

select e.*, d.dname
from emp e left outer join dept d
on e.deptno=d.deptno
where e.job=(select job from emp where ename='庞统')

select e.ename, e.sal, d.dname
from ename e left outer join deptno d
on e.deptno=d.deptno
where e.sal>(select max(sal) from emp where deptno=30)

select * from tb_year
year  zz
2000  100
2001  150
2002  250
2003  300
select y1.* ifnull(concat((y1.zz-y2.zz)/y2.zz * 100, '%'), '0%') 增长比
from tb_year y1 left outer join tb_year y2
on y1.year=y2.year+1