Question

I have the following table

| id | title    | parent |
------------------------
|  1 | example  |   0    |
|  2 | example2 |   2    |
   3   example3     3
   4   example4     2
   5   example5     2

How can I make a query in function of title field to get back all the row where parent_id’s values are equal.

example: show all rows having the same parent as the row which matches title="example2".

should give back

2 | example2 | 2
4 | example4 | 2
5 | example5 | 2

Answer 1

When you only have the title as argument and want all the rows that are related to the same parent_id you may utilize a subquery:

SELECT * FROM tbl WHERE parent IN (SELECT parent FROM tbl WHERE title = "example2")

or you can basically achieve the same using a self-join:

SELECT related.* 
FROM tbl source
LEFT JOIN tbl related ON source.parent = related.parent
WHERE source.title = "example2"