for r1 in (select rows from table_1 where colx = {value}) loop
    for r2 in (select rows from table_2 that match current row from table_1) loop
        output values from current row of table_1 and current row of table_2
    end loop
end loop

def nl_join(outer_table, inner_table):
    for o in get_from(outer_table, ...): 
        for i in get_from(inner_table, 'id = $1', i.id): # 1й аргумент - источник, 2й - условие, 3й - аргумент условия
             yield o, i
                
def hash_join(build_table, prob_table):
    # создаем hash таблицу:
    hash_build_table = {o.id : (hash(o.id) as hash_key,o.*) for o in build_table}    
    for i in get_from(prob_table, ...): 
        for j in get_from(hash_build_table, 'hash_key=$1', hash(i.id)):
            if i.id = j.id:
                yield j, i

SQL> get tests/1
  1  explain plan for
  2  with t as (select/*+ materialize */ 1 a, rpad('x',111,'x') b from dual connect by level<=100)
  3* select * from t t1, t t2 where t1.a=t2.a

Plan hash value: 1434490737

----------------------------------------------------------------------------------------------------------------------
| Id  | Operation                                | Name                      | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                         |                           |     1 |   120 |     6   (0)| 00:00:01 |
|   1 |  TEMP TABLE TRANSFORMATION               |                           |       |       |            |          |
|   2 |   LOAD AS SELECT (CURSOR DURATION MEMORY)| SYS_TEMP_0FD9D68B5_257369 |       |       |            |          |
|*  3 |    CONNECT BY WITHOUT FILTERING          |                           |       |       |            |          |
|   4 |     FAST DUAL                            |                           |     1 |       |     2   (0)| 00:00:01 |
|*  5 |   HASH JOIN                              |                           |     1 |   120 |     4   (0)| 00:00:01 |
|   6 |    VIEW                                  |                           |     1 |    60 |     2   (0)| 00:00:01 |
|   7 |     TABLE ACCESS FULL                    | SYS_TEMP_0FD9D68B5_257369 |     1 |    70 |     2   (0)| 00:00:01 |
|   8 |    VIEW                                  |                           |     1 |    60 |     2   (0)| 00:00:01 |
|   9 |     TABLE ACCESS FULL                    | SYS_TEMP_0FD9D68B5_257369 |     1 |    70 |     2   (0)| 00:00:01 |
----------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   3 - filter(LEVEL<=100)
   5 - access("T1"."A"="T2"."A")