PL/SQL中的%type类型变量

关于%type的例子
declare 
v_ename test.ename%type;
v_sal test.sal%type;
c_tax_rate constant number(3,2):=0.03;
v_tax_sal v_sal%type;
begin
select ename,sal into v_ename,v_sal
from test where empno=&eno;
v_tax_sal:=v_sal*c_tax_rate;
dbms_output.put_line('雇员名:'||v_ename);
dbms_output.put_line('雇员工资:'||v_sal);
dbms_output.put_line('所得税:'||v_tax_sal);
end;