Question

I want to write a map-like object type in PL/SQL. What I mean is a key-value-pair list, where a value can be another key-value-pair list. Simple, or so I thought. Here are the two simplified

CREATE OR REPLACE TYPE TKey AS OBJECT
(
    name varchar2(240),
    value_text varchar2(2000),
    value_map TMap
)

CREATE OR REPLACE TYPE TMap AS TABLE OF TKey

Maybe not so simple, because now I have a “Chicken or the egg”-problem. If I put TKey in first, he will complain that TMap is not defined. If I put in TMap first, he will complain that TKey is not defined. If I put TKey in and leave out the value_map line, then add the TMap type, then try to replace the TKey type, he will not allow it.

Am I out of luck? Is such a construct not possible in PL/SQL?

Thanks in advance

Clarification:
What I want is something, that can give me this:
A map containing the keys a, b, and c. The value of a is the varchar “hello”, the value of b is the varchar “world”, and the value of c is another map, with the keys x and y, and the value of x being “what’s” and the value of y being “up”.

This is what it would look like in Java:

Map<String, Object> map = new HashMap<String, Object>();
map.set("a", "Hello");
map.set("b", "World");
Map<String, Object> child = new HashMap<String, Object>();
child.set("x", "What's");
child.set("y", "up");
map.set("c", child);

Now I know that something like “object” as being able to store anything is not possible. What I need is an object that can store a list of objects being of the same type as this object. So basically, a tree, yeah.

Answer 1

Perhaps you need to think more relationally 🙂

Instead of storing a TMap (value_map) inside the TKey type, just store value_map_name, which can then be used to lookup another entry in the table.

CREATE OR REPLACE TYPE TKey AS OBJECT(
 name varchar2(240),
 value_text varchar2(2000),
 value_map_name varchar2(240));

Then you can use associative arrays (as per mamboking’s answer) to store them.