How can I define a type in oracle11g that references a collection of that type?

问题

I want to do something like this

create type Item as object (
    id number,
    subitems table of ref Item
)

but oracle throws an exception when I try to do it. Is this possible, and if yes then how?

回答1:

Oracle will not compile your definition because the type Item hasn't been compiled yet. Why dont you give this a try:

Compile this:

CREATE OR REPLACE TYPE Item;

CREATE OR REPLACE TYPE items_table IS TABLE OF REF item;

and then try:

CREATE OR REPLACE TYPE item AS OBJECT (
   id number,
   subitems items_table
)

回答2:

That would be nice wouldn't it! You could try this:

create type item_ids_t is table of number;

create type Item as object (
   id number,
   subitems item_ids_t);

Which means that subitems is just a list of ids, which would then be used to look up a table indexed by id.

来源：https://stackoverflow.com/questions/1054896/how-can-i-define-a-type-in-oracle11g-that-references-a-collection-of-that-type