数据库小练习：

CREATE TABLE emp(
empno INT,
ename VARCHAR(20),
job VARCHAR(20),
mgr VARCHAR(20),
hiredate DATE,
sal DOUBLE,
comm DOUBLE,
deptno VARCHAR(10)
)
SELECT * FROM emp;
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1001,'甘宁','文员',1013,'2000-12-17',8000.00,20);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,comm,deptno) VALUES (1002,'黛绮丝','销售员',1006,'2001-02-20',16000.00,3000.00,30);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,comm,deptno) VALUES (1003,'殷天正','销售员',1006,'2001-02-22',12500.00,5000.00,30);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1004,'刘备','经理',1009,'2001-04-02',29750.00,20);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,comm,deptno) VALUES (1005,'谢逊','销售员',1006,'2001-09-28',12500.00,14000.00,30);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1006,'关羽','经理',1009,'2001-05-01',28500.00,30);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1007,'张飞','经理',1009,'2001-09-01',24500.00,10);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1008,'诸葛亮','分析师',1004,'2007-04-19',30000.00,20);
INSERT INTO emp (empno,ename,job,hiredate,sal,deptno) VALUES (1009,'曾阿牛','董事长','2001-11-17',50000.00,10);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,comm,deptno) VALUES (1010,'韦一笑','销售员',1006,'2001-09-08',15000.00,0.00,30);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1011,'周泰','文员',1008,'2007-05-23',11000.00,20);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1012,'程普','文员',1006,'2001-12-03',9500.00,30);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1013,'庞统','分析师',1004,'2001-12-03',30000.00,20);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,deptno) VALUES (1014,'黄盖','文员',1007,'2002-01-23',13000.00,10);
INSERT INTO emp (empno,ename,job,mgr,hiredate,sal,comm,deptno) VALUES (1015,'张三','保洁员',1001,'2013-05-01',80000.00,50000.00,50);