oracle PLS-00363: 表达式 'A1' 不能用作赋值目标

create or replace procedure helloworld(a1 in number,a2 in number,sum out number,sub out number)

as

begin

a1:=100;

sum:=a1+a2;

dbms_output.put_line(a1);

end;

/

create or replace procedure helloworld(a1 in number,a2 in number,sum out number,sub out number)

as

begin

sum:=a1+a2;

dbms_output.put_line(a1);

end;

/

传入的是产量不是变量，所以a1,a2不能重新赋值

但是sum,sub可以他们是输出参数