alter sequence g restart with 0;
recreate table inv( id int primary key, req_id int, mvz int, unique(req_id, mvz) using index inv_req_mvz_unq );
commit;
insert into inv values( gen_id(g,1), 2, 200);
insert into inv values( gen_id(g,1), 2, 203);
insert into inv values( gen_id(g,1), 2, 201);

insert into inv values( gen_id(g,1), 1, 103);
insert into inv values( gen_id(g,1), 1, 101);

insert into inv values( gen_id(g,1), 3, 303);
insert into inv values( gen_id(g,1), 3, null);
insert into inv values( gen_id(g,1), 3, 301);

insert into inv values( gen_id(g,1), 4, 400);
insert into inv values( gen_id(g,1), 4, 403);
insert into inv values( gen_id(g,1), 4, 401);
insert into inv values( gen_id(g,1), 4, 404);
commit;


set term ^;
create or alter procedure check_identical(
  a_req_id int,
  a_mvz1 int,
  a_mvz2 int,
  a_mvz3 int
)
returns(is_identical smallint)
as
begin
    for
        with recursive
        inp as (
            --select 2 as a_req_id, 200 as a_mvz1, 201 as a_mvz2, 203 as a_mvz3
            --select 1 as a_req_id, 100 as a_mvz1, 101 as a_mvz2, 103 as a_mvz3
            --select 3 as a_req_id, null as a_mvz1, 301 as a_mvz2, 303 as a_mvz3
            --select 4 as a_req_id, 401 as a_mvz1, 402 as a_mvz2, 404 as a_mvz3
            select :a_req_id as a_req_id, :a_mvz1 as a_mvz1, :a_mvz2 as a_mvz2, :a_mvz3 as a_mvz3
            from rdb$database
        )
        ,n as (select 1 k from rdb$database union all select u.k+1 from n u where u.k<3)
        ,u as(
            select i.a_req_id as rq, decode(n.k, 1, i.a_mvz1, 2, i.a_mvz2, 3, i.a_mvz3) mv
            from inp i, n
        )
        ,d as (
            select rq, mv from u
            union all
            select v.req_id, v.mvz from inv v join inp i on v.req_id = i.a_req_id
        )
        --select * from d
        ,e as(
            select d.rq,d.mv,count(*) c
            from d
            group by d.rq,d.mv
            having count(*)<>2
            rows 1
        )
        select iif( exists(select * from e), 0, 1 ) as is_identical
        from rdb$database
        into is_identical
    do suspend;
end
^ set term ;^
commit;

SQL> select * from inv;

          ID       REQ_ID          MVZ
============ ============ ============
           1            2          200
           2            2          203
           3            2          201
           4            1          103
           5            1          101
           6            3          303
           7            3       <null>
           8            3          301
           9            4          400
          10            4          403
          11            4          401
          12            4          404

SQL> select * from check_identical(2, 200, 201, 203);

IS_IDENTICAL
============
           1

SQL> select * from check_identical(2, 200, null , 203);

IS_IDENTICAL
============
           0

SQL> select * from check_identical(1, 101, 103, null);

IS_IDENTICAL
============
           0

SQL> select * from check_identical(3, null, 303, 301);

IS_IDENTICAL
============
           1

SQL> select * from check_identical(4, 400, 403, 401);

IS_IDENTICAL
============
           0