Query with union condition - php

Question

Does anyone know how can I write a query to get the desired result to be like tools/lift planning/cranimax from this database
resource_category_id category_name parent_category
1 Tools 0
2 product literature 0
3 Terms and Conitions 0
4 crane library 1
5 geniune 1
6 lift planning 1
8 cranimax 6
For this I wrote a query like this which is not completed, for example this is thing am having in my mind if I choose from cranimax it's having a parent_category 6 so it should make union with that row having resource_category_id and that row having parent_category 1 it should repeat until parent category 0 occurs.
$data['breadcrumbs'] = $this->Manito_model->get_breadcrumbs_details($resource_id);
public function get_breadcrumbs_details($resource_id)
{
$query=$this->db->query("select * from resource_category as m WHERE m.resource_category_id = $resource_id union (select * from resource_category where parent_category != 0) as m2 on m.parent_category = m2.resource_parent_category");
return $query->result();
}
i expect my result to be like this
array (size=3)
0 =>
object(stdClass)[35]
public 'resource_category_id' => string '8' (length=1)
public 'category_name' => string 'cranimax' (length=8)
public 'parent_category' => string '6' (length=1)
public 'created_at' => string '2017-11-04 13:59:39' (length=19)
1 =>
object(stdClass)[35]
public 'resource_category_id' => string '6' (length=1)
public 'category_name' => string 'lift planning' (length=8)
public 'parent_category' => string '1' (length=1)
public 'created_at' => string '2017-11-04 13:59:39' (length=19)
2 =>
object(stdClass)[35]
public 'resource_category_id' => string '1' (length=1)
public 'category_name' => string 'Tools' (length=8)
public 'parent_category' => string '0' (length=1)
public 'created_at' => string '2017-11-04 13:59:39' (length=19)

Answer 1

UNION is used to combine the result from multiple SELECT statements into a single result set (ie making it extremely simple: you need to do two select, but you want only one result, then you make a union)
In you situation you don't need a UNION, but a simple JOIN which "complete" your results with other data:
select m.*, m2.category_name AS parent_name FROM resource_category AS m LEFT JOIN resource_category m2 ON m2.resource_category_id = m.resource_parent_category WHERE m.resource_category_id = $resource_id