Consider the example:

MariaDB [test]> CREATE TABLE cs1 (d1 DECIMAL(38))engine=Columnstore;
Query OK, 0 rows affected (0.388 sec)

MariaDB [test]> CREATE TABLE cs2 (de1 DECIMAL(38,1))engine=Columnstore;
Query OK, 0 rows affected (0.376 sec)

MariaDB [test]> SELECT cs2.de1, cs1.d1 FROM cs1 INNER JOIN cs2 ON cs1.d1 = cs2.de1 ORDER BY 1;
ERROR 1815 (HY000): Internal error: IDB-1002: 'cs1' and 'cs2' have incompatible column type specified for join condition.
}
MDB is able to join using columns with unequal scales.