Employees表和Departments表的定义如下: Employees表: Column Datatype Constraint Emp_id Number Primary Key Emp_name varchar2 Not null Salary number Check (salary between 1000 and 12000) Designamtion varchar2 Not null Detpartment_id Number References Departments(Dept_id) Departments表: Column Datatype Constraint Dept_id Number Primary Key Dept_name varchar2 Not null Location varchar2 Not null Detpartment_id Number References Departments(Dept_id) on delete cascade