How to perform such SQL?

[Heorhii Hryhoriev]

There is a table "Categories".

category_id | parent_id
------------------------
1| NULL
2| 1
3| 2
4| 3
5| NULL
6| 5

The parent_id field contains the ID of the parent category for each category.
I need to create a query that will return all rows from a category table except the one given and all of its child categories.

For example,
for category_id 1, should be selected lines with category_id [5, 6]
for category_id 2, should be selected lines with category_id [1, 5, 6]
for category_id 3, should be selected lines with category_id [1, 2, 5, 6]
for category_id 4, should be selected lines with category_id [1, 2, 3, 5, 6]
for category_id 5, should be selected lines with category_id [1, 2, 3, 4]
for category_id 6, should be selected lines with category_id [1, 2, 3, 4, 5]

If a category has parent_id is NULL, it means that it has no parent category.