SELECT * 

FROM (

SELECT DISTINCT items_6. * , cm1.brand AS brand1, cm2.model AS model1

FROM items_6

LEFT JOIN cars_models AS cm1 ON cm1.brandid = items_6.brand

LEFT JOIN cars_models AS cm2 ON cm2.id = items_6.model

) t

GROUP BY t.id

Query 1 - bad results:

SELECT items_6 . * , cm1.brand AS brand1, cm2.model AS model1

FROM items_6

LEFT JOIN cars_models AS cm1 ON cm1.brandid = items_6.brand

LEFT JOIN cars_models AS cm2 ON cm2.id = items_6.model

GROUP BY items_6.id

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

| id | brand | model | imported | brand1 | model1 |

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

| 28 |    54 |   618 |        0 | NULL   | NULL   |

| 29 |    65 |  1133 |        0 | NULL   | NULL   |

| 30 |   123 |     0 |        0 | NULL   | NULL   |

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

Query 2 - good results, but not unique by items_6.id:

SELECT DISTINCT items_6 . * , cm1.brand AS brand1, cm2.model AS model1

FROM items_6

LEFT JOIN cars_models AS cm1 ON cm1.brandid = items_6.brand

LEFT JOIN cars_models AS cm2 ON cm2.id = items_6.model

GROUP BY items_6.id

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

| id | brand | model | imported | brand1     | model1 |

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

| 28 |    54 |   618 |        0 | NULL       | NULL   |

| 29 |    65 |  1133 |        0 | Volkswagen | Touran |

| 29 |    65 |  1133 |        0 | VW         | Touran |

| 30 |   123 |     0 |        0 | NULL       | NULL   |

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

EXPLAIN EXTENDED

SELECT DISTINCT items_6 . * , cm1.brand AS brand1, cm2.model AS model1

FROM items_6

LEFT JOIN cars_models AS cm1 ON cm1.brandid = items_6.brand

LEFT JOIN cars_models AS cm2 ON cm2.id = items_6.model

GROUP BY items_6.id;

SHOW WARNINGS;

EXPLAIN EXTENDED SELECT items_6 . * , cm1.brand AS brand1, cm2.model AS model1 FROM items_6 LEFT JOIN cars_models AS cm1 ON cm1.brandid = items_6.brand LEFT JOIN cars_models AS cm2 ON cm2.id = items_6.model GROUP BY items_6.id;

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

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

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

|    1 | SIMPLE      | items_6 | index  | NULL          | PRIMARY | 4       | NULL               |    3 |   100.00 |             |

|    1 | SIMPLE      | cm1     | ref    | brandid       | brandid | 2       | test.items_6.brand |   11 |   100.00 | Using where |

|    1 | SIMPLE      | cm2     | eq_ref | PRIMARY       | PRIMARY | 2       | test.items_6.model |    1 |   100.00 | Using where |

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

| Note  | 1003 | select `test`.`items_6`.`id` AS `id`,`test`.`items_6`.`brand` AS `brand`,`test`.`items_6`.`model` AS `model`,`test`.`items_6`.`imported` AS `imported`,`test`.`cm1`.`brand` AS `brand1`,`test`.`cm2`.`model` AS `model1` from `test`.`items_6` left join `test`.`cars_models` `cm1` on(((`test`.`cm1`.`brandid` = `test`.`items_6`.`brand`) and (`test`.`items_6`.`brand` is not null))) left join `test`.`cars_models` `cm2` on(((`test`.`cm2`.`id` = `test`.`items_6`.`model`) and (`test`.`items_6`.`model` is not null))) where 1 group by `test`.`items_6`.`id` |