Create Tables and Nested Tables:

 create or replace type type_table_rec is object
(
    col_seqno number, 
    table_col_name varchar2(100),
    table_name varchar2(100)
);

create or replace type nested_table_rec is table of type_table_rec;

create or replace type type_table_name is table of varchar2(100);

create sequence query_gen_seq;

create table query_generate_log(
    request_id number primary key,
    seq_id number,
    status varchar2(50),
    message_tx varchar2(4000),
    created_by varchar2(200) default sys_context('USERENV','OS_USER'),
    creation_date date default sysdate
); 
 
 create table query_joins
  (seq_no number primary key,
   table_name varchar2(4000),
   join_condition varchar2(4000),
   description varchar2(4000),
   created_by varchar2(200) default sys_context('USERENV','OS_USER'),
    creation_date date default sysdate);