select a from t1, t2 where b between 1 and 2 and a in (select b from t2);

select a from t1 join t2 on b between 1 and 2 and a in (select b from t2);

MariaDB [test]> explain

    -> select a from t1, t2 where b between 1 and 2 and a in (select b from t2);

+------+-------------+-------+-------+---------------+------+---------+-----------+------+--------------------------------------------------------------+

| id   | select_type | table | type  | possible_keys | key  | key_len | ref       | rows | Extra                                                        |

+------+-------------+-------+-------+---------------+------+---------+-----------+------+--------------------------------------------------------------+

|    1 | PRIMARY     | t1    | ALL   | NULL          | NULL | NULL    | NULL      |    7 | Using where                                                  |

|    1 | PRIMARY     | t2    | ref   | idx           | idx  | 5       | test.t1.a |  256 | Using index; FirstMatch(t1)                                  |

|    1 | PRIMARY     | t2    | range | idx           | idx  | 5       | NULL      |    2 | Using where; Using index; Using join buffer (flat, BNL join) |

+------+-------------+-------+-------+---------------+------+---------+-----------+------+--------------------------------------------------------------+

MariaDB [test]> explain 

    -> select a from t1 join t2 on b between 1 and 2 and a in (select b from t2);

+------+--------------------+-------+----------------+---------------+------+---------+------+------+-------------------------------------------------+

| id   | select_type        | table | type           | possible_keys | key  | key_len | ref  | rows | Extra                                           |

+------+--------------------+-------+----------------+---------------+------+---------+------+------+-------------------------------------------------+

|    1 | PRIMARY            | t2    | range          | idx           | idx  | 5       | NULL |    2 | Using where; Using index                        |

|    1 | PRIMARY            | t1    | ALL            | NULL          | NULL | NULL    | NULL |    7 | Using where; Using join buffer (flat, BNL join) |

|    2 | DEPENDENT SUBQUERY | t2    | index_subquery | idx           | idx  | 5       | func |  256 | Using index                                     |

+------+--------------------+-------+----------------+---------------+------+---------+------+------+-------------------------------------------------+

create table t1 (a int) engine=myisam;

insert into t1  values (5),(3),(2),(7),(2),(5),(1); 

create table t2 (b int, index idx(b)) engine=myisam;

insert into t2 values (2),(3),(2),(1),(3),(4);

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

insert into t2 select b+10 from t2;

analyze table t1,t2;

explain select a from t1, t2 where b between 1 and 2 and a in (select b from t2);

explain select a from t1 join t2 on b between 1 and 2 and a in (select b from t2);