How to use right join correctly - mysql

Question

Table Locations
loc_id loc_name hier2 hier3 hier4 hier5 hier6 hier7 hier8 hier9
152675 Castelli 105 109 0 319 14356 152673 152675 0
14356 Rome 105 109 0 319 14356 0 0 0
...
Table Lacations References
oid name loc_id
12 Demo Villa 152675
...
Now i try to find some entries a user searches by entering the string "caste":
SELECT geo.loc_id, geo.loc_name AS name
FROM locations AS geo
LEFT JOIN locations AS geoh3 ON geo.hier3 = geoh3.loc_id
LEFT JOIN locations AS geoh4 ON geo.hier4 = geoh4.loc_id
LEFT JOIN locations AS geoh8 ON geo.hier8 = geoh8.loc_id
WHERE geo.loc_name LIKE 'caste%'
GROUP BY geo.loc_name
This works. I get the entry with loc_id 152675
Now i only want to get those entrys we have objects in. So i join the reference table:
SELECT geo.loc_id, geo.loc_name AS name
FROM locations AS geo
LEFT JOIN locations AS geoh3 ON geo.hier3 = geoh3.loc_id
LEFT JOIN locations AS geoh4 ON geo.hier4 = geoh4.loc_id
LEFT JOIN locations AS geoh8 ON geo.hier8 = geoh8.loc_id
RIGHT JOIN locations_xref AS gx ON geo.loc_id = gx.loc_id
WHERE geo.loc_name LIKE 'caste%'
GROUP BY geo.loc_name
This works. Again i get the location entry with loc_id 152675 because theres a reference.
PROBLEM
Now the user searches for "rome". I dont get any entry because there is no object reference directly to the city "Rome". The existing object is referenced to a district of rome.
As you can see the district and the city entries have hierarchy IDs which can be used to identify the correct structure. I just cant get it to work together with the reference table, so i only get those objects which are in "rome" or in a district, which is part of rome.
Any help is greatly appreciated!

Answer 1

I don't know much about your data but from first sight it seems that hier6 has the information about relationship between Rome and Castelli. So the query you need may look something more or less like this:
SELECT geo.loc_id, geo.loc_name AS name
FROM locations AS geo
LEFT JOIN locations AS geoh3 ON geo.hier3 = geoh3.loc_id
LEFT JOIN locations AS geoh6 ON geo.hier6 = geoh6.loc_id
LEFT JOIN locations AS geoh4 ON geo.hier4 = geoh4.loc_id
LEFT JOIN locations AS geoh8 ON geo.hier8 = geoh8.loc_id
RIGHT JOIN locations_xref AS gx ON geo.loc_id = gx.loc_id
WHERE geoh6.loc_name LIKE 'rome%'
GROUP BY geo.loc_name

Answer 2

You can tweak your query (as Karolis suggested), but I don't think that will give you what you want. Your query will return 'Castelli' when you search for 'Rome%', but it won't return 'Rome'. It won't return 'Rome', because 'Rome' isn't in your xref table.
To return 'Rome' with this kind of query, you'll need to insert a row for 'Rome' into the xref table.
You can get all the things that are "in" Rome with a UNION, but it doesn't reference your xref table at all.
select la.loc_id, la.loc_name
from locations la
where la.loc_name like 'Rome%'
union
select lb.loc_id, lb.loc_name
from locations lb
inner join locations lc on lc.hier6 = lb.hier6
It's not clear to me how you determine which column to use for the join at run time.
Later . . .
If you don't know which columns to use at run time, you have to LEFT JOIN on all of them. And since you don't know whether the search string might refer to a value joined through column hier2, hier3, hier4, etc., then you have to check each of those columns for a match, too.
If locations_xref acts like a filter, then you need an inner join on that table, along with a row for 'Rome'. (Because you have properties in Rome.) Probably something along these lines.
SELECT geo.loc_id, geo.loc_name AS name
FROM locations AS geo
LEFT JOIN locations AS geoh2 ON geo.hier2 = geoh2.loc_id
LEFT JOIN locations AS geoh3 ON geo.hier3 = geoh3.loc_id
LEFT JOIN locations AS geoh4 ON geo.hier4 = geoh4.loc_id
LEFT JOIN locations AS geoh5 ON geo.hier5 = geoh5.loc_id
LEFT JOIN locations AS geoh6 ON geo.hier6 = geoh6.loc_id
LEFT JOIN locations AS geoh7 ON geo.hier7 = geoh7.loc_id
LEFT JOIN locations AS geoh8 ON geo.hier8 = geoh8.loc_id
LEFT JOIN locations AS geoh9 ON geo.hier9 = geoh9.loc_id
INNER JOIN locations_xref lx on lx.loc_id = geo.loc_id
WHERE geo.loc_name LIKE 'Rom%'
or geoh2.loc_name like 'Rom%'
or geoh3.loc_name like 'Rom%'
or geoh4.loc_name like 'Rom%'
or geoh5.loc_name like 'Rom%'
or geoh6.loc_name like 'Rom%'
or geoh7.loc_name like 'Rom%'
or geoh8.loc_name like 'Rom%'
or geoh9.loc_name like 'Rom%'
Before you get too invested in this model, you should take a look at Bill Karwin's database antipatterns. "Naive Trees" starts on slide 48.