with tblA (id,name) as (
select 1,'name1'  from dual union all
select 2,'name2' from dual 
)

select * from tblA;

with tblB (id,name) as (
select 1,'name1'  from dual union all
select 2,'name2' from dual
)

select * from tblB;

with tblC (idA,idB) as (
select 1, 1  from dual union all
)

select * from tblC;

-- здесь ошибка.
insert into tblC values (idA, idB)
values ((select id from tblA where name = 'name1'), (select id from tblB where name = 'name1'))

insert into tblC
  (idA, idB)
  select t1.idA,
         t2.idB
    from (select tblA.rid as idA
            from tblA
           where tblA.name = 'name1') t1,
         (select tblB.rid as idB
            from tblB
           where tblB.name = 'name1') t2
   where rownum = 1