[转]Oracle 数组的学习

提叻一个代码段，要人帮助解释一下。
代码段如下：

declare
type t_indexby is table of number
index by binary_integer;
type t_nested is table of number;
type t_varray is varray(10) of number;
v_indexby t_indexby;
v_nested t_nested;
v_varray t_varray;
begin
v_indexby(1):=1;
v_indexby(2):=2;
v_nested:=t_nested(1,2,3,4,5);
v_varray:=t_varray(1,2);
end;