MySQL Multiple Table Join
- by hitman001
I have a 3 tables that I'm trying to join and get distinct results.
CREATE TABLE `car` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`id`)
) ENGINE=InnoDB
mysql> select * from car;
+----+-------+
| id | name |
+----+-------+
| 1 | acura |
+----+-------+
CREATE TABLE `tires` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`tire_desc` varchar(255) DEFAULT NULL,
`car_id` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`),
KEY `new_fk_constraint` (`car_id`),
CONSTRAINT `new_fk_constraint` FOREIGN KEY (`car_id`) REFERENCES `car` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB
mysql> select * from tires;
+----+-------------+--------+
| id | tire_desc | car_id |
+----+-------------+--------+
| 1 | front_right | 1 |
| 2 | front_left | 1 |
+----+-------------+--------+
CREATE TABLE `lights` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`lights_desc` varchar(255) NOT NULL,
`car_id` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`),
KEY `new1_fk_constraint` (`car_id`),
CONSTRAINT `new1_fk_constraint` FOREIGN KEY (`car_id`) REFERENCES `car` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB
mysql> select * from lights;
+----+-------------+--------+
| id | lights_desc | car_id |
+----+-------------+--------+
| 1 | right_light | 1 |
| 2 | left_light | 1 |
+----+-------------+--------+
Here is my query.
mysql> SELECT name, group_concat(tire_desc), group_concat(lights_desc)
FROM car
left join tires on car.id = tires.car_id
left join lights on car.id = car_id
group by car.id;
+-------+-----------------------------------------------+-----------------------------------------------+
| name | group_concat(tire_desc) | group_concat(lights_desc) |
+-------+-----------------------------------------------+-----------------------------------------------+
| acura | front_right,front_right,front_left,front_left | right_light,left_light,right_light,left_light |
+-------+-----------------------------------------------+-----------------------------------------------+
I get duplicate entires and this is what I would like to get.
+-------+-----------------------------------------------+--------------------------------+
| name | group_concat(tire_desc) | group_concat(lights_desc) |
+-------+-----------------------------------------------+--------------------------------+
| acura | front_right,front_left | right_light,left_light |
+-------+-----------------------------------------------+--------------------------------+
I cannot use distinct in group_concat because I might have legitimate duplicates which I would like to keep. Is there any way to do this query using joins and not using inner selects like the statement below?
SELECT name,
(select group_concat(tire_desc) from tires where car.id = tires.car_id),
(select group_concat(lights_desc) from lights where car.id = lights.car_id)
FROM car
Also, if I will use inner selects, will there be any performance issues over joins?
