Laravel & MySQL having a join on a join? - mysql

Question

I need to join a table on a already joined table cause the data I need from the other table is also spread in another table. This is my SQL model so far:
Now I need to join the addresses table the joined child table as well cause I need the address of each child as well. My only problem is, how can I join the table addresses based on the childs.address_id?
I have already tried to to this:
INNER JOIN `addresses` AS `addresse_child` ON `childs`.`address_id` = `addresses`.`id`
Sadly not working..
My SQL Query so far (DB::getQueryLog())
SELECT `assignments`.`id` AS `assignment_id`,
`assignments`.`persons` AS `assignment_persons`,
`assignments`.`start_date` AS `assignment_start_date`,
`assignments`.`end_date` AS `assignment_end_date`,
`addresses`.`id` AS `address_id`,
`addresses`.`first_name` AS `address_first_name`,
`addresses`.`last_name` AS `address_last_name`,
`addresses`.`company` AS `address_company`,
`childs`.`id` AS `child_id`,
`childs`.`address_id` AS `child_address_id`,
`childs`.`sibling_id` AS `child_sibling_id`,
`childs`.`height` AS `child_height`,
`childs`.`weight` AS `child_weight`
FROM `assignments`
INNER JOIN `addresses` ON `assignments`.`address_id` = `addresses`.`id`
INNER JOIN `childs` ON `assignments`.`id` = `childs`.`assignment_id`
WHERE `assignments`.`deleted_at` IS NULL
AND `addresses`.`deleted_at` IS NULL
AND `childs`.`deleted_at` IS NULL
My Laravel SQL command:
$assignment_data = DB::table('assignments')
->join('addresses', 'assignments.address_id', '=', 'addresses.id')
->join('childs', 'assignments.id', '=', 'childs.assignment_id')
->select(
'assignments.id as assignment_id',
'assignments.persons as assignment_persons',
'assignments.start_date as assignment_start_date',
'assignments.end_date as assignment_end_date',
'addresses.id as address_id',
'addresses.first_name as address_first_name',
'addresses.last_name as address_last_name',
'addresses.company as address_company',
'childs.id as child_id',
'childs.address_id as child_address_id',
'childs.sibling_id as child_sibling_id',
'childs.height as child_height',
'childs.weight as child_weight'
)
->whereNull('assignments.deleted_at')
->whereNull('addresses.deleted_at')
->whereNull('childs.deleted_at')
->get();

Answer 1

You should be able to do;
SELECT `assignments`.`id` AS `assignment_id`,
`assignments`.`persons` AS `assignment_persons`,
`assignments`.`start_date` AS `assignment_start_date`,
`assignments`.`end_date` AS `assignment_end_date`,
`addresses`.`id` AS `address_id`,
`addresses`.`first_name` AS `address_first_name`,
`addresses`.`last_name` AS `address_last_name`,
`addresses`.`company` AS `address_company`,
`childs`.`id` AS `child_id`,
`childs`.`address_id` AS `child_address_id`,
`childs`.`sibling_id` AS `child_sibling_id`,
`childs`.`height` AS `child_height`,
`childs`.`weight` AS `child_weight`
FROM `assignments`
INNER JOIN `addresses` ON `assignments`.`address_id` = `addresses`.`id`
INNER JOIN `childs` ON `assignments`.`id` = `childs`.`assignment_id` AND
`childs`.`address_id` = `addresses`.`id`
WHERE `assignments`.`deleted_at` IS NULL
AND `addresses`.`deleted_at` IS NULL
AND `childs`.`deleted_at` IS NULL
And in Laravel this can be achieved by doing;
$assignment_data = DB::table('assignments')
->join('addresses', 'assignments.address_id', '=', 'addresses.id')
->join('childs', function($q) {
$q->on('assignments.id', '=', 'childs.assignment_id')
->where('childs.address_id', '=', 'addresses.id');
})
->select(
'assignments.id as assignment_id',
'assignments.persons as assignment_persons',
'assignments.start_date as assignment_start_date',
'assignments.end_date as assignment_end_date',
'addresses.id as address_id',
'addresses.first_name as address_first_name',
'addresses.last_name as address_last_name',
'addresses.company as address_company',
'childs.id as child_id',
'childs.address_id as child_address_id',
'childs.sibling_id as child_sibling_id',
'childs.height as child_height',
'childs.weight as child_weight'
)
->whereNull('assignments.deleted_at')
->whereNull('addresses.deleted_at')
->whereNull('childs.deleted_at')
->get();
However you should note that by doing INNER JOINS you will only get results if there are rows in each table. You maybe better off doing LEFT JOINS instead, depending on how your data is required.