Properly populating tables in an Object Relational database
I've got a homework assignment that requires that I use Oracle 10g Express to implement an Object Relational database to track phone billing data. I have a superclass of Communications with subclasses of Call, Text, and Data. I'm hitting a snag with properly populating these tables so that I can find the appropriate data in the various tables.
My Types and Tables are declared as such:
create type CommunicationType as object (
-- column names here
) not final;
create type CallType under CommunicationType (
-- column names here
);
create type TextType under CommunicationType (
-- column names here
);
create type DataType under CommunicationType (
-- column names here
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create table Communications of CommunicationType (
-- Primary and Foreign key constraints here
);
create table Calls of CallType;
create table Texts of TextType;
create table Datas of DataType;
When I try to insert
data into one of the subclasses, its entry doesn't appear in the superclass. Likewise if I insert
into the superclass, it doesn't show up in the appropriate subclass. For example, insert into Calls values (CallType( -- Values -- ));
doesn't show any data in Communications. Nor does insert into Communications values (CallType( -- Values -- ));
show anything in Calls.
What am I doing wrong?
You have created four separate tables. If you insert a row into one table, there is no reason to expect to see your row in another table.
Your tables based on CallType
, TextType
and DataType
inherit their structure and behaviour from CommunicationType
, but this doesn't mean that the data is replicated. I suspect you probably don't need the table Communications
at all.
< aside > Personally, if I'm using the Oracle database I'd forego using object types entirely and just model the thing using a pure Relational model, but that's probably just me - and doesn't help you much since your teacher seems to expect you to implement an "Object Relational" database... :)
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