Postgres join when only one row is equal - postgresql

Question

I have two tables and I am wanting to do an inner join between table_1 and table_2 but only when there is one row in table_2 that meets the join criteria.
For example:
table_1
id | name | age |
-----------------+------------------+--------------+
1 | john jones | 10 |
2 | pete smith | 15 |
3 | mary lewis | 12 |
4 | amy roberts | 13 |
table_2
id | name | age | hair | height |
-----------------+------------------+--------------+--------------+--------------+
1 | john jones | 10 | brown | 100 |
2 | john jones | 10 | blonde | 132 |
3 | mary lewis | 12 | brown | 146 |
4 | pete smith | 15 | black | 171 |
So I want to do a join when name is equal, but only when there is one corresponding matching name in table_2
So my results would look like this:
id | name | age | hair |
-----------------+------------------+--------------+--------------+
2 | pete smith | 15 | black |
3 | mary lewis | 12 | brown |
As you can see, John Jones isn't in the results as there are two corresponding rows in table_2.
My initial code looks like this:
select tb.id,tb.name,tb.age,sc.hair
from table_1 tb
inner join table_2 sc
on tb.name = sc.name and tb.age = sc.age
Can I apply a clause within the join so that it only joins on rows which are unique matches?

Answer 1

Group by all columns and apply having count(*) = 1
select tb.id,tb.name,tb.age,sc.hair
from table_1 tb
join table_2 sc
on tb.name = sc.name and tb.age = sc.age
group by tb.id,tb.name,tb.age,sc.hair
having count(*) = 1
The interesting thing to note is that you don’t need the aggregate expression (in the case count(*) )in the select clause.