Handle null in sql SELECTS with JOIN ON - mysql

Question

Lets put I have these 3 tables:
main table:
ID | OtherStuff1 | OtherStuff2 | IdProvince | IdTown
-----+-------------+-------------+------------+--------
1 | Stuff1 | Stuff2 | NULL | 1
-----+-------------+-------------+------------+--------
2 | Stuff3 | Stuff4 | 1 | NULL
province table:
ID | ProvinceName
---+--------------
1 | ProvName1
town table:
ID | TownName
---+--------------
1 | TwName1
Then I use one of these sql to print the information so it appears the name instead of the Id number.
SELECT a.Id, OtherStuff1, OtherStuff2, ProvinceName, TownName
FROM main AS a
LEFT JOIN (province AS b, town AS c)
ON (a.IdProvince = b.Id AND a.IdTown = c.Id)
WHERE a.IdProvince=1;
or
SELECT a.Id, OtherStuff1, OtherStuff2, ProvinceName, TownName
FROM main AS a
LEFT JOIN (province AS b, town AS c)
ON (a.IdProvince = b.Id AND a.IdTown = c.Id)
WHERE a.IdTown=1;
The problem comes that when it prints the result it comes like this:
ID | OtherStuff1 | OtherStuff2 | ProvinceName | TownName
-----+-------------+-------------+--------------+--------
1 | Stuff1 | Stuff2 | NULL | NULL
If one of the id's is put in NULL then even if there are other id's with numbers it puts NULL too. How do I avoid that without just delete the join of that column that is null likes this:
SELECT a.Id, OtherStuff1, OtherStuff2, ProvinceName, IdTown
FROM main AS a
LEFT JOIN (province AS b)
ON (a.IdProvince = b.Id)
WHERE a.IdProvince=1;
This would work if IdTown is NULL but I don't want this solution because there are much many rows and a lot other columns with Id's and it's impossible to go one by one checking which one is NULL and which one is not.
So I want a query like this but when there is a null it doesn't mess the other Id's putting all of them in NULL.
SELECT a.Id, OtherStuff1, OtherStuff2, ProvinceName, TownName
FROM main AS a
LEFT JOIN (province AS b, town AS c)
ON (a.IdProvince = b.Id AND a.IdTown = c.Id)
WHERE a.IdProvince=1;
Sorry the expected result for this query would be like this:
ID | OtherStuff1 | OtherStuff2 | ProvinceName | TownName
-----+-------------+-------------+--------------+--------
2 | Stuff1 | Stuff2 | ProvName1 | NULL
Any ideas?
Thanks in advance for the help!

Answer 1

don't mix join notations (a from clause should avoid the use of , if you're using the ANSI92 standards. If using the ANSI 89 standards, then there should be no left join syntax)
I see no reason not to do two left joins back to main table (A) one for Province and one for Town...
.
SELECT a.Id, OtherStuff1, OtherStuff2, ProvinceName, TownName
FROM main AS a
LEFT JOIN province AS b
ON a.IdProvince = b.Id
LEFT JOIN town as c
ON a.IdTown = c.Id
WHERE a.IdProvince=1;

Answer 2

This is because the condition in your ON clause:
a.IdProvince = b.Id AND a.IdTown = c.Id
Here you are asking to LEFT JOIN 2 tables only when both conditions are met, which in your case they don't.
I would try to keep the 2 joins separate like so:
SELECT a.Id, OtherStuff1, OtherStuff2, b.ProvinceName, c.TownName
FROM main AS a
LEFT JOIN province AS b ON (a.IdProvince = b.Id)
LEFT JOIN town AS c ON (a.IdTown = c.Id)
WHERE a.IdProvince = 1;