PL / SQL继承行类型

Question

I know Oracle PL/SQL allows to create object sub type using the "under" keyword. But is it possible to create a subtype that inherit the RowType of a particular table?

For example, if there is a table named Customer and I want to create an object type that has all attributes in Customer table with extra fields.

I tried:

create or replace type t_sub_type as object under Customer%RowType (
  price NUMBER
);

Of course, the code fails to compile. So is there any way to achieve this?

Answer 1

Not unless customer happens to be an object table. If customer is a regular old table, customer%rowtype is a record, not an object, so it cannot be inherited from. If you created an object type customer_typ and created a table customer of those object types, then you could create a subtype of customer_typ . Something like

SQL> ed
Wrote file afiedt.buf

  1  create type customer_typ
  2    as object (
  3      name varchar2(100),
  4      address varchar2(1000),
  5      phone varchar2(30)
  6    )
  7*   not final
SQL> /

Type created.

SQL> create table customer_tbl of customer_typ;

Table created.

SQL> create type subcustomer_typ
  2    under customer_typ (
  3      newColumn number
  4    );
  5  /

Type created.

SQL> desc subcustomer_typ;
 subcustomer_typ extends SCOTT.CUSTOMER_TYP
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 NAME                                               VARCHAR2(100)
 ADDRESS                                            VARCHAR2(1000)
 PHONE                                              VARCHAR2(30)
 NEWCOLUMN                                          NUMBER

Of course, I'm hard pressed to imagine a case where this would make a great deal of sense. But it is possible. If you can describe why you want to inherit from a %rowtype record, we may be able to suggest some alternative approaches.