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+笔记
+
+show variables; 显示系统所有变量
+
+rollback;回滚，条件关闭自动提交off或者0
+
+show variables like 'autocommit';查看开启隐式事务（自动提交）
+
+commit;确认操作手动提交无法回滚
+
+
+create database zuoye charset utf8;
+use zuoye;
+
+-- 部门表
+create table dept(
+	deptno int primary key auto_increment, -- 部门编号
+	dname varchar(14) ,	  -- 部门名字
+	loc varchar(13)   -- 地址
+) ;
+-- 员工表
+create table emp(
+	empno int primary key auto_increment,-- 员工编号
+	ename varchar(10), -- 员工姓名										-
+	job varchar(9),	-- 岗位
+	mgr int,	 -- 直接领导编号
+	hiredate date, -- 雇佣日期，入职日期
+	sal int, -- 薪水
+	comm int,  -- 提成
+	deptno int not null, -- 部门编号
+	foreign key (deptno) references dept(deptno)
+);
+insert into dept values(10,'财务部','北京');
+insert into dept values(20,'研发部','上海');
+insert into dept values(30,'销售部','广州');
+insert into dept values(40,'行政部','深圳');
+insert into emp values(7369,'刘一','职员',7902,'1980-12-17',800,null,20);
+insert into emp values(7499,'陈二','推销员',7698,'1981-02-20',1600,300,30);
+insert into emp values(7521,'张三','推销员',7698,'1981-02-22',1250,500,30);
+insert into emp values(7566,'李四','经理',7839,'1981-04-02',2975,null,20);
+insert into emp values(7654,'王五','推销员',7698,'1981-09-28',1250,1400,30);
+insert into emp values(7698,'赵六','经理',7839,'1981-05-01',2850,null,30);
+insert into emp values(7782,'孙七','经理',7839,'1981-06-09',2450,null,10);
+insert into emp values(7788,'周八','分析师',7566,'1987-06-13',3000,null,20);
+insert into emp values(7839,'吴九','总裁',null,'1981-11-17',5000,null,10);
+insert into emp values(7844,'郑十','推销员',7698,'1981-09-08',1500,0,30);
+insert into emp values(7876,'郭十一','职员',7788,'1987-06-13',1100,null,20);
+insert into emp values(7900,'钱多多','职员',7698,'1981-12-03',950,null,30);
+insert into emp values(7902,'大锦鲤','分析师',7566,'1981-12-03',3000,null,20);
+insert into emp values(7934,'木有钱','职员',7782,'1983-01-23',1300,null,10);
+
+
+
+
+-- 1、列出最低薪金大于1500的各种工作。
+select job from emp where sal>1500;
+-- 2、列出在部门 "销售部" 工作的员工的姓名，假定不知道销售部的部门编号。
+select d.dname,e.ename from emp e join dept d on e.deptno = d.deptno where d.dname='销售部';
+-- 3、列出薪金高于公司平均薪金的所有员工。
+SELECT * FROM emp;
+WITH
+a as 
+(select distinct ename,avg(sal) over() from emp)
+SELECT DISTINCT * from emp e,a where e.ename>a.ename;
+-- 4、列出与"周八"从事相同工作的所有员工。
+SELECT * FROM emp;
+WITH
+a as 
+(select ename,job from emp where ename='周八')
+select * from emp e,a where e.job=a.job;
+-- 5、列出薪金等于部门30中员工的薪金的所有员工的姓名和薪金。
+SELECT * FROM emp;
+WITH
+a as 
+(select sal,deptno from emp where deptno=30)
+select distinct ename,e.sal from emp e,a where e.deptno=a.deptno;
+-- 6、列出薪金高于在部门30工作的所有员工的薪金的员工姓名和薪金。
+SELECT * FROM emp;
+WITH
+a as 
+(select distinct max(sal) over() as n from emp where deptno=30)
+select distinct ename,e.sal from emp e,a where e.sal>a.n;
+-- 7、列出在每个部门工作的员工数量、平均工资、平均服务年限。
+select count(*),avg(sal),avg(datediff(now(),hiredate))/365 from emp GROUP BY deptno;
+-- 8、列出所有员工的姓名、部门名称和工资。
+select e.ename,d.dname,e.sal from emp e join dept d on e.deptno=d.deptno;
+-- 9、列出所有部门的详细信息和部门人数。
+ select distinct d.*,count(*) over(partition by dname) from emp e join dept d on e.deptno=d.deptno;
+-- 10、列出各种工作的最低工资。
+select distinct job,min(sal) over() from emp;
+-- 11、列出各个部门的 经理 的最低薪金。
+select distinct ename,min(sal) over() from emp where job='经理';
+-- 12、列出所有员工的年工资,按年薪从低到高排序。 
+select ename,(sal+ifnull(comm,0))*12 as b from emp ORDER BY b desc;