3 level nesting tables in SQL - sql

Question

I wanted to create following 3 - level structure using Oracle object programming aspects:
- Bosses
- - Managers
- - - Employees
When I want to run script for creating table tab_univ_bosses following exception occurs in last line:
Error at Command Line:31 Column:3
Error report:
SQL Error: ORA-22913: "must specify table name for nested table column or attribute"
*Cause: The storage clause is not specified for a nested table column
or attribute.
*Action: Specify the nested table storage clause for the nested table
column or attribute.
Error starting at line 33 in command:
NESTED TABLE managers STORE AS tab_univ_managers
Error report:
Unknown Command
This is my code:
-- TYPE <EMPLOYEE>
create or replace
TYPE type_Employee AS OBJECT (
name VARCHAR2(30),
department_name VARCHAR2(30),
second_name VARCHAR2(30),
manager REF type_Employee
);
CREATE or replace TYPE type_ListEmployees
AS TABLE OF type_Employee;
-- TYPE <MANAGER>
create or replace
TYPE type_Manager AS OBJECT (
userData type_Employee,
manager REF type_Employee,
listEmployees type_ListEmployees
);
NESTED TABLE listEmployees STORE AS tab_univ_employees
CREATE or replace TYPE type_ListManagers
AS TABLE OF type_ListEmployees;
-- BASE TABLE
CREATE TABLE tab_univ_bosses (
id NUMBER PRIMARY KEY,
userData type_Employee,
managers type_ListManagers
);
NESTED TABLE managers STORE AS tab_univ_managers <--- There is a problem...

Answer 1

You can do this using a single table:
create or replace
TYPE type_Employee AS OBJECT (
name VARCHAR2(30),
department_name VARCHAR2(30),
second_name VARCHAR2(30),
manager REF type_Employee
);
/
CREATE TABLE Employees OF type_Employee (
manager SCOPE IS Employees
)
/
INSERT INTO Employees VALUES ( 'Big', 'Admin', 'Boss', NULL );
INSERT INTO Employees VALUES ( 'Middle', 'Accounts', 'Manager', ( SELECT REF(e) FROM Employees e WHERE name = 'Big' AND second_name = 'Boss' ) );
INSERT INTO Employees VALUES ( 'Other', 'Sales', 'Manager', ( SELECT REF(e) FROM Employees e WHERE name = 'Big' AND second_name = 'Boss' ) );
INSERT INTO Employees VALUES ( 'Junior', 'Accounts', 'Accountant', ( SELECT REF(e) FROM Employees e WHERE name = 'Middle' AND second_name = 'Manager' ) );
INSERT INTO Employees VALUES ( 'Junior', 'Sales', 'Salesman', ( SELECT REF(e) FROM Employees e WHERE name = 'Other' AND second_name = 'Manager' ) );
-- Get everyone in hierarchical order.
SELECT name, second_name, department_name, LEVEL
FROM Employees e
START WITH manager IS NULL
CONNECT BY PRIOR name = DEREF( e.MANAGER ).name
AND PRIOR second_name = DEREF( e.MANAGER ).second_name
ORDER SIBLINGS BY name, second_name;
-- Get the employees which have the manager: 'Middle', 'Manager'
SELECT name, second_name, department_name
FROM Employees e
WHERE DEREF( e.Manager ).Name = 'Middle'
AND DEREF( e.Manager ).Second_Name = 'Manager';
However if you really want to use that structure then:
create or replace
TYPE type_Employee AS OBJECT (
name VARCHAR2(30),
department_name VARCHAR2(30),
second_name VARCHAR2(30),
manager REF type_Employee
);
/
CREATE or replace TYPE type_ListEmployees
AS TABLE OF type_Employee;
/
create or replace
TYPE type_Manager AS OBJECT (
userData type_Employee,
manager REF type_Employee,
listEmployees type_ListEmployees
);
/
CREATE or replace TYPE type_ListManagers
AS TABLE OF type_Manager;
/
CREATE TABLE tab_univ_bosses (
id NUMBER PRIMARY KEY,
userData type_Employee,
managers type_ListManagers
)
NESTED TABLE managers STORE AS tab_univ_managers (
NESTED TABLE listEmployees STORE AS tab_univ_employees
);
/