Question

I have an table in my MySql database that has the following columns:

- id
- parent_id
- visible

Basically if I have a table populated like this:

    id     name      parent_id      visible
    ------ --------- -------------- -------
    1      Admin     0              1
    2      Review    0              0
    3      Archive   2              1
    4      Support   0              1

Though the hierarchy is…

1 - Admin
2 - Review
   3 - Archive
4 - Support

I would like Archive (3) to essentially inherit the ‘visible’ attribute from it’s parent row — Review (2). I’d like to return this in a view like this:

    id     name      parent_id      visible
    ------ --------- -------------- -------
    1      Admin     0              1
    2      Review    0              0
    3      Archive   2              0
    4      Support   0              1

Does anyone know if this is possible in MySql without resorting to a stored procedure?

Thanks!

Answer 1

You can do this in a normal query using a CASE statement for the visible column:

select a.id, a.name, a.parent_id,
       CASE WHEN a.parent_id = 0 
       then a.visible
       else b.visible
       end as visible
from myTable a
left join myTable b on a.parent_id = b.id

You could also create the view (same code):

create view myTableView as
select a.id, a.name, a.parent_id,
       CASE WHEN a.parent_id = 0 
       then a.visible
       else b.visible
       end as visible
from myTable a
left join myTable b on a.parent_id = b.id