How to join on two fields where one could be null - sql-server

Question

This query may seem basic, but i'm at a fairly basic level.
So here is my data - Sorry about the formatting, i've tried following the help but the table formatting is obviously not working for me (Can someone please advise?):
Table 1
ID |Country
---| -------
1 | UK
1 | IE
1 | US
2 | UK
2 | FR
Table 2
ID |Country
---| -------
1 | UK
1 | IE
2 | UK
The result i want is this
Table 1----- | ----Table 2
ID |Country |-----ID |Country
---| ------- |--------|--------
1 | UK | 1 | UK
1 | IE | 1 | IE
1 | US | 1 | NULL
2 | UK | 2 | UK
2 | FR | 2 | NULL
But more specifically i want to identify the NULL's so that i get this result
Table 1----- | ----Table 2
ID |Country |-----ID |Country
---| ------- |--------|--------
1 | US | 1 | NULL
2 | FR | 2 | NULL
The code i have used so far is:
select *
from table1 t1
left outer join table2 t2 on t1.id = t2.id and t1.country = t2.country
where t1.id is not null
and t2.country is null

Answer 1

Try this
select t1.id, t1.country, isnull(t2.id, t1.id) AS T2_ID, t2.country
from table1 t1
left outer join table2 t2 on t1.id = t2.upc and t1.country = t2.country
if you want to only show the ones where you have nulls in t2, you can add
where t2.id is null
But if you want to show all the records, just leave it without the WHERE condition

Answer 2

You were close, you just need to use isnull() or coalesce().
select
t1.id
, t1.country
, t2_Id = isnull(t2.id,t1.id)
, t2_country = t2.country
from table1 t1
left outer join table2 t2 on t1.id = t2.id and t1.country = t2.country
where t1.id is not null
--and t2.country is null
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returns:
+----+---------+-------+------------+
| id | country | t2_Id | t2_country |
+----+---------+-------+------------+
| 1 | UK | 1 | UK |
| 1 | IE | 1 | IE |
| 1 | US | 1 | NULL |
| 2 | UK | 2 | UK |
| 2 | FR | 2 | NULL |
+----+---------+-------+------------+
with the additional filter of t2.country is null
returns:
+----+---------+-------+------------+
| id | country | t2_Id | t2_country |
+----+---------+-------+------------+
| 1 | US | 1 | NULL |
| 2 | FR | 2 | NULL |
+----+---------+-------+------------+
The main difference between the two is that coalesce() can support more than 2 parameters, and it selects the first one that is not null. More differences between the two are answered here.
coalesce() is standard ANSI sql, so it is available in most RDBMS. isnull() is specific to sql server.
Reference:
isnull() - msdn
coalesce() - msdn
coalesce vs isnull - Itzik Ben-Gan