05：修改数据时不能违反外键约束
为表HRMAN。Departments的DEP_id列和表HRMAN.Employees的DEP_ID列中创建外键约束
ALTER TABLE HRMAN.Employees
ADD CONSTRAINT FK_EMP_DEPID
FOREIGN KEY(Dep_id) REFERENCES HRMAN.Departments(Dep_id);
UPDATE HRMAN.Employees SET Dep_id=200 WHERE Emp_Name='张三';
应用场景206：删除数据语句
DELETE FROM HRMAN.Employees WHERE Emp_Name = '小明';
TRUNCATE TABLE HRMAN.Employees;