一 示例数据 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 -- table employee drop table if exists employee; create table employee( empno int, ename VARCHAR(10), job VARCHAR(9), mgr int, hiredate DATE, sal decimal(7,2), comm decimal(7,2), deptno int ) ; insert into employee (empno, ename,