Oracle function return select query

oralce_function_return_select_query.sql

CREATE TABLE product (
    col1 VARCHAR2(255),
    col2 NUMBER,
    col3 VARCHAR2(255),
    col4 NUMBER
);

INSERT INTO product (col1, col2, col3, col4)
VALUES ('A', 1, 'AA', 10);
INSERT INTO product (col1, col2, col3, col4)
VALUES ('C', 2, 'CC', 20);
INSERT INTO product (col1, col2, col3, col4)
VALUES ('B', 3, 'BB', 30);

CREATE TABLE employee (
    col1 VARCHAR2(255),
    col2 NUMBER,
    col3 VARCHAR2(255),
    col4 NUMBER
);

INSERT INTO employee (col1, col2, col3, col4)
VALUES ('X', 10, 'XX', 1);
INSERT INTO employee (col1, col2, col3, col4)
VALUES ('Y', 20, 'YY', 2);
INSERT INTO employee (col1, col2, col3, col4)
VALUES ('Z', 30, 'ZZ', 3);


CREATE OR REPLACE TYPE T_RECORD AS OBJECT (
    col1 VARCHAR2(255),
    col2 NUMBER,
    col3 VARCHAR2(255),
    col4 NUMBER
);

CREATE OR REPLACE TYPE T_TABLE AS TABLE OF T_RECORD;

CREATE OR REPLACE FUNCTION return_table RETURN T_TABLE AS
    v_ret T_TABLE;
BEGIN
    SELECT T_RECORD(e.col1, e.col2 * 100, e.col3, e.col4 * 100) BULK COLLECT INTO
        v_ret
    FROM employee e;

    RETURN v_ret;
END return_table;

SELECT * FROM TABLE (return_table());

INSERT INTO product (col1, col2, col3, col4) (SELECT * FROM TABLE (return_table()));